call it quits

1 agree or acknowledge that terms are now equal, especially on the settlement of a debt.

2 decide to abandon an activity or venture, especially so as to cut your losses.

☞ The origin of the -s in quits is uncertain: the word may be an abbreviation of the medieval Latin quittus, meaning 'discharged', which was used on receipts to indicate that something had been paid for. The phrase is recorded from the late 19th century, but an earlier form, cry quits, dates back to the mid 17th century.