An Etymological Dictionary of Astronomy and Astrophysics

1a) Go away from.

1b) To let remain or have remaining behind after going, disappearing, ceasing, etc.

2a) Permission to be absent, as from work or military duty.

2b) The time this permission lasts (Dictionary.com).

Etymology (EN): M.E. leven, from O.E. laefan “to allow to remain in the same state or condition” (cf. O.Saxon farlebid “left over;” Ger. bleiben “to remain”) ultimately from PIE *leip- “to stick, adhere;” also “fat,” from which the cognates: Gk. lipos “fat;” O.E. lifer “liver,” → life.

Etymology (PE): Parižidan, on the model of
Sariqoli barēzj “leavings;” Yaghnobi piraxs- “to stay behind, remain;” ultimately from Proto-Ir. *apa-raic-, from *raic- “to abandon, leave;” cf. Av. raēc- “to leave, let” (Cheung 2006), → heritage.