If you call this with argument "unused=true" it searches for the translation strings that exist in en_US but are never used.
IMPORTANT: that can take quite a lot of time (up to 10 minutes), you need to tune the max_execution_time on your php.ini accordingly.

Duplicate strings in lang files in /home/libellules/public_html/gestion/elenad/dev/translation/../../htdocs/langs/en_US/ - 91 found

#StringFile and lines
28NewAssetTypeassets.lang (24 - New asset type) (64 - New asset type)
49NotTheAssignedApproverholiday.lang (74 - You are not the assigned approver) (98 - You are not the assigned approver)
89Receptionreceptions.lang (4 - Reception) (7 - Product reception)
90Receptionsreceptions.lang (5 - Receptions) (8 - Reception)
2ByYearaccountancy.lang (192 - By year)
main.lang (775 - By year)
25Eventsagenda.lang (12 - Events)
main.lang (878 - Events)
51StatusInterInvoicedinterventions.lang (30 - Billed)
main.lang (494 - Invoiced)
52Closedmain.lang (142 - Closed)
ticket.lang (66 - Closed)
53NewObjectmain.lang (211 - New %s)
modulebuilder.lang (9 - New object)
54Typemain.lang (215 - Type)
ticket.lang (70 - Type)
55MulticurrencyPaymentAmountmain.lang (358 - Payment amount, original currency)
multicurrency.lang (19 - Payment amount, original currency)
56Categorymain.lang (472 - Tag/category)
ticket.lang (71 - Analytic code)
57OpenAllmain.lang (497 - Open (All))
stocks.lang (150 - Open for all actions)
58NotReadmain.lang (648 - Not read)
ticket.lang (59 - Not read)
4InternalUseradmin.lang (48 - Internal user)
users.lang (68 - Internal user)
5NewModuleadmin.lang (207 - New)
modulebuilder.lang (8 - New module)
6NoticePeriodadmin.lang (265 - Notice period)
holiday.lang (110 - Notice period)
7LanguageFileadmin.lang (362 - Language file)
modulebuilder.lang (50 - File for language)
8Stringadmin.lang (403 - String)
members.lang (101 - String)
9Intadmin.lang (406 - Integer)
members.lang (103 - Int)
10DateAndTimeadmin.lang (408 - Date and hour)
members.lang (104 - Date and time)
11Fieldadmin.lang (478 - Field)
blockedlog.lang (2 - Field)
exports.lang (60 - Field)
12Upgradeadmin.lang (1013 - Upgrade)
install.lang (104 - Upgrade)
13Serveradmin.lang (1024 - Server)
install.lang (49 - Server)
14DatabaseServeradmin.lang (1026 - Database host)
install.lang (52 - Database server)
15DatabaseNameadmin.lang (1027 - Database name)
install.lang (53 - Database name)
16DriverTypeadmin.lang (1035 - Driver type)
install.lang (48 - Driver type)
17CompanyNameadmin.lang (1056 - Name)
companies.lang (26 - Company name)
18WithdrawalsSetupadmin.lang (1535 - Setup of module Direct Debit payments)
withdrawals.lang (22 - Direct debit payment setup)
19Buyadmin.lang (1616 - Buy)
products.lang (50 - Purchase)
20Selladmin.lang (1617 - Sell)
products.lang (49 - Sell)
21AccountancyCodeadmin.lang (1620 - Accounting Code)
companies.lang (305 - Accounting account)
22CashDeskadmin.lang (1643 - Point of Sale)
cashdesk.lang (3 - Point of sale)
23ByDefaultInListadmin.lang (1790 - Show by default on list view)
categories.lang (89 - By default in list)
1LineIdaccountancy.lang (124 - Id line)
exports.lang (41 - Id of line)
3CustomerInvoicePaymentaccountancy.lang (208 - Payment of invoice customer)
banks.lang (100 - Customer payment)
24AffectedToagenda.lang (10 - Assigned to)
projects.lang (111 - Allocated to)
26Locationagenda.lang (16 - Location)
stocks.lang (34 - Location)
27InterventionSentByEMailagenda.lang (82 - Intervention %s sent by email)
interventions.lang (38 - Intervention %s sent by email)
29DeleteTypeassets.lang (29 - Delete)
members.lang (76 - Delete)
30ShowTypeCardassets.lang (32 - Show type '%s')
members.lang (144 - Show type '%s')
31IBANbanks.lang (32 - IBAN number)
bills.lang (430 - IBAN)
32BICbanks.lang (33 - BIC/SWIFT code)
bills.lang (431 - BIC/SWIFT)
33StandingOrdersbanks.lang (38 - Direct Debit orders)
bills.lang (234 - Direct debit orders)
34StandingOrderbanks.lang (39 - Direct debit order)
bills.lang (235 - Direct debit order)
35Accountbanks.lang (64 - Account)
compta.lang (15 - Account)
36SubscriptionPaymentbanks.lang (102 - Subscription payment)
members.lang (158 - Subscription payment)
37NoSupplierOrderboxes.lang (67 - No recorded purchase order)
orders.lang (78 - No purchase order)
38ShowCompanycashdesk.lang (29 - Show company)
companies.lang (321 - Show Third Party)
39Historycashdesk.lang (65 - History)
suppliers.lang (6 - History)
40DeleteFromCatcategories.lang (82 - Remove from tags/category)
compta.lang (247 - Remove from accounting group)
41Customercommercial.lang (4 - Customer)
companies.lang (267 - Customer)
42Prospectcommercial.lang (6 - Prospect)
companies.lang (265 - Prospect)
propal.lang (12 - Prospect)
43ShowTaskcommercial.lang (18 - Show task)
projects.lang (39 - Show task)
44ToPaycompta.lang (66 - To pay)
paybox.lang (14 - Do payment)
45ContractStatusClosedcontracts.lang (9 - Closed)
products.lang (78 - Closed)
46ExportsAreaexports.lang (2 - Exports)
other.lang (255 - Exports area)
47ExportableDatasexports.lang (6 - Exportable dataset)
other.lang (259 - Exportable data)
48AvailableFormatsexports.lang (27 - Available Formats)
other.lang (256 - Available formats)
50CreateUserinstall.lang (60 - Create user account or grant user account permission on the Dolibarr database)
users.lang (30 - Create user)
59OrderDateorders.lang (10 - Order date)
suppliers.lang (9 - Order date)
60CreatedByother.lang (109 - Created by %s)
ticket.lang (149 - Created by)
61FollowingUrlAreAvailableToMakePaymentspaybox.lang (4 - Following URLs are available to offer a page to a customer to make a payment on Dolibarr objects)
stripe.lang (5 - Following URLs are available to offer a page to a customer to make a payment on Dolibarr objects)
62PaymentFormpaybox.lang (5 - Payment form)
stripe.lang (6 - Payment form)
63WelcomeOnPaymentPagepaybox.lang (6 - Welcome to our online payment service)
stripe.lang (7 - Welcome to our online payment service)
64ThisScreenAllowsYouToPaypaybox.lang (7 - This screen allow you to make an online payment to %s.)
stripe.lang (8 - This screen allow you to make an online payment to %s.)
65ThisIsInformationOnPaymentpaybox.lang (8 - This is information on payment to do)
stripe.lang (9 - This is information on payment to do)
66ToCompletepaybox.lang (9 - To complete)
stripe.lang (10 - To complete)
67YourEMailpaybox.lang (10 - Email to receive payment confirmation)
stripe.lang (11 - Email to receive payment confirmation)
68Creditorpaybox.lang (11 - Creditor)
stripe.lang (13 - Creditor)
69PaymentCodepaybox.lang (12 - Payment code)
stripe.lang (14 - Payment code)
70Continuepaybox.lang (16 - Next)
stripe.lang (17 - Next)
71ToOfferALinkForOnlinePaymentpaybox.lang (17 - URL for %s payment)
stripe.lang (18 - URL for %s payment)
72ToOfferALinkForOnlinePaymentOnOrderpaybox.lang (18 - URL to offer a %s online payment user interface for a sales order)
stripe.lang (19 - URL to offer a %s online payment user interface for a sales order)
73ToOfferALinkForOnlinePaymentOnInvoicepaybox.lang (19 - URL to offer a %s online payment user interface for a customer invoice)
stripe.lang (20 - URL to offer a %s online payment user interface for a customer invoice)
74ToOfferALinkForOnlinePaymentOnContractLinepaybox.lang (20 - URL to offer a %s online payment user interface for a contract line)
stripe.lang (21 - URL to offer a %s online payment user interface for a contract line)
75ToOfferALinkForOnlinePaymentOnFreeAmountpaybox.lang (21 - URL to offer a %s online payment user interface for a free amount)
stripe.lang (22 - URL to offer a %s online payment user interface for a free amount)
76ToOfferALinkForOnlinePaymentOnMemberSubscriptionpaybox.lang (22 - URL to offer a %s online payment user interface for a member subscription)
stripe.lang (23 - URL to offer a %s online payment user interface for a member subscription)
77YouCanAddTagOnUrlpaybox.lang (24 - You can also add url parameter <b>&tag)
stripe.lang (24 - You can also add url parameter <b>&tag)
78AccountParameterpaybox.lang (28 - Account parameters)
stripe.lang (26 - Account parameters)
79UsageParameterpaybox.lang (29 - Usage parameters)
stripe.lang (27 - Usage parameters)
80InformationToFindParameterspaybox.lang (30 - Help to find your %s account information)
stripe.lang (28 - Help to find your %s account information)
81VendorNamepaybox.lang (32 - Name of vendor)
stripe.lang (30 - Name of vendor)
82CSSUrlForPaymentFormpaybox.lang (33 - CSS style sheet url for payment form)
stripe.lang (31 - CSS style sheet url for payment form)
83Stockproducts.lang (45 - Stock)
stocks.lang (18 - Stock)
84Stocksproducts.lang (47 - Stocks and location (warehouse) of products)
stocks.lang (19 - Stocks)
85Movementsproducts.lang (48 - Movements)
stocks.lang (23 - Movements)
86Suppliersproducts.lang (83 - Vendors)
suppliers.lang (2 - Vendors)
87ListOfStockMovementsproducts.lang (90 - List of stock movements)
stocks.lang (26 - List of stock movements)
88Unitproducts.lang (165 - Unit)
stocks.lang (41 - Unit)
91NewUserticket.lang (271 - New user)
users.lang (29 - New user)