Guard
late Middle English (in the sense ‘care, custody’): from Old French garde (noun), garder (verb), of West Germanic origin. Compare with ward.
wiktionary
For verb: From early Middle French or late Old French (circa 14th cent) guarder(“to keep, ward, guard, save, preserve, etc.”), from Frankish *wardōn, from Proto-Germanic *wardāną(“to guard, protect”). Cognate with Old English weardian (whence Englishto ward). Compare French garder. See also English regard.
For noun: From Middle English garde, from early Middle French or late Old French guarde(“a guardian, warden, keeper”) (whence modern French garde), from the verb guarder. Doublet of garda, which is from Irish.
etymonline
guard (n.)
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.
guard (v.)
mid-15c., from guard (n.) or from Old French garder "to keep watch over, guard, protect, maintain, preserve" (corresponding to Old North French warder, see gu-), from Frankish *wardon, from Proto-Germanic *wardon "to guard" (from PIE root *wer- (3) "perceive, watch out for"). Italian guardare, Spanish guardar also are from Germanic. Related: Guarded; guarding.