early 13c., "freed from dregs or lees" (of ale, wine, etc.), probably literally "having stood long enough to clear," ultimately from PIE root *sta- "to stand" (see stet); probably via Old French estal "placed, fixed position," from Frankish *stal- "position" (see stall, n.1). Cognate with Middle Dutch stel "stale" (of beer and old urine). Originally a desirable quality (in beer and wine); the meaning "not fresh" is first recorded late 15c. Figurative sense (of immaterial things) "old and trite, hackneyed" is recorded from 1560s. As a noun, "that which has become tasteless by exposure," hence "a prostitute" (in Shakespeare, etc.). Related: Staleness.

mid-15c., from stale, adj.. Related: Staled; staling.