safeguard n.

c. 1300, sauf, "unscathed, unhurt, uninjured; free from danger or molestation, in safety, secure; saved spiritually, redeemed, not damned;" from Old French sauf "protected, watched-over; assured of salvation," from Latin salvus "uninjured, in good health, safe," which is related to salus "good health," saluber "healthful" (all from PIE *solwos from root *sol- "whole, well-kept"). For the phonological development of safe from sauf, OED compares gage from Old North French gauge.

From late 14c. as "rescued, delivered; protected; left alive, unkilled." The meaning "not exposed to danger" (of places, later of valuables) is attested from late 14c.; in reference to actions, etc., the meaning "free from risk," is recorded by 1580s. The sense of "sure, reliable, not a danger" is from c. 1600. The sense of "conservative, cautious" is from 1823. It has been paired alliteratively with sound (adj.) from c. 1300. In Middle English it also meant "in good health," also "delivered from sin or damnation." Related: Safeness.

early 15c., "one who keeps watch, a body of soldiers," also "care, custody, guardianship," and the name of a part of a piece of armor, from French garde "guardian, warden, keeper; watching, keeping, custody," from Old French garder "to keep, maintain, preserve, protect" (see guard (v.)). Abstract or collective sense of "a keeping, a custody" (as in bodyguard) also is from early 15c. Sword-play and fisticuffs sense is from 1590s; hence to be on guard (1640s) or off (one's) guard (1680s). As a football position, from 1889. Guard-rail attested from 1860, originally on railroad tracks and running beside the rail on the outside; the guide-rail running between the rails.