c. 1200, quaier, "a short book;" mid-15c., "a set of four folded pages for a book; pamphlet consisting of a single quire," original senses now obsolete, from Anglo-French quier, Old French quaier, caier "sheet of paper folded in four" (Modern French cahier), from Medieval Latin quaternum, "set of four sheets of parchment or paper," from Vulgar Latin *quaternus, from Latin quaterni "four each," from quater "four times" (from PIE root *kwetwer- "four").
Meaning "standard unit for selling paper" (lately typically 24 or 25 sheets, the twentieth part of a ream) is recorded from late 14c. In quires (mid-15c.) means "unbound."
an early form and later variant spelling of choir (q.v.), Middle English, from Old French quer, queor, variants of cuer, and compare Medieval Latin quorus, variant of chorus.