英语词源字典 - 在线词源网站

stalk (v.1)[stalk 词源字典]: "pursue stealthily," Old English -stealcian, as in bestealcian "to steal along, walk warily," from Proto-Germanic *stalkon, frequentative of PIE *stel-, possibly a variant of *ster- (3) "to rob, steal" (see steal (v.)). Compare hark/hear, talk/tell). In another view the Old English word might be from a sense of stalk (v.1), influenced by stalk (n.). Meaning "harass obsessively" first recorded 1991. Related: Stalked; stalking.

A stalking-horse in literal use was a horse draped in trappings and trained to allow a fowler to conceal himself behind it to get within range of the game; figurative sense of "person who participates in a proceeding to disguise its real purpose" is recorded from 1610s.[stalk etymology, stalk origin, 英语词源]
unwary (adj.): by 1570s, possibly late 14c., from un- (1) "not" + wary (adj.). Old English had unwær "incautious," unwærlic. Related: Unwarily.
wary (adj.): late 15c., with -y (2) + ware, from Old English wær "prudent, aware, alert, wary," from Proto-Germanic *waraz (cognates: Old Norse varr "attentive," Gothic wars "cautious," Old Saxon giwar, Middle Dutch gheware, Old High German giwar, German gewahr "aware"), from PIE root *wer- (4) "to perceive, watch out for" (see ward (n.)). Related: Warily; wariness.