call it quits

2. call it quits,
   1. to end one’s activity, especially temporarily: At 10 o’clock I decided to call it quits for the day.
   2. to abandon an effort.
3. cry quits, to agree to end competition and consider both sides equal: It became too dark to continue play and they decided to cry quits.

“even” (with another), 1660s; earlier “discharged of a liability” (c.1200), perhaps from Medieval Latin quittus (see quit (adj.)).

Stop working, abandon something, give up, as in John is calling it quits for now or This ground is far too stony for a garden so I’m calling it quits. This idiom comes from cry quits, dating from the 1600s and meaning “declare even” or “get even.” The verb call was substituted in the late 1800s. Also see call it a day.