labile (adj.)

mid-15c., "elapsing of time, expiration;" also "temporary forfeiture of a legal right" due to some failure or non-action by the holder, from Old French laps "lapse," from Latin lapsus "a slipping and falling, a landslide; flight (of time); falling into error," from labi "to glide, slip, slide, sink, fall; decline, go to ruin," which is of unknown etymology.

Meaning "moral transgression, sin" is from c. 1500; that of "slip of the memory" is 1520s; that of "a falling away from one's faith" is from 1650s.