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mid-15c., "elapsing of time, expiration;" also "temporary forfeiture of a legal right," from Middle French laps "lapse," from Latin lapsus "a slipping and falling, flight (of time), falling into error," from labi "to slip, glide, fall." Meaning "moral transgression, sin" is c.1500; that of "slip of the memory" is 1520s; that of "a falling away from one's faith" is from 1650s.
early 15c., said to be from lapse (n.) or from Latin lapsare "to lose one's footing." Related: Lapsed; lapses; lapsing.