"stem of a plant," early 14c., probably a dim. (with -k suffix) of stale "one of the uprights of a ladder, handle, stalk," from O.E. stalu "wooden part" (as of a harp), from P.Gmc. *stalo; related to O.E. steala "stalk, support," and steall "place" (see stall (2)).
"pursue stealthily," O.E. -stealcian, as in bestealcian "to steal along," from P.Gmc. *stalkojanan, probably from a frequentative of the root of steal (cf. hark from hear, talk from tell). Or it may be from a sense of stalk (v.1), influenced by
stalk (n.). Meaning "harass obsessively" first recorded 1991. Stalker earlier meant "a poacher" (1424) and "one who prowls for purposes of theft" (1508). A stalking-horse was lit. a horse trained to allow a fowler to conceal himself behind it to get within range of the game; fig. sense of "person who participates in a proceeding to disguise its real purpose" is recorded from 1612.
"walk haughtily" (opposite meaning of stalk (v1.)) is 1530, perhaps from stalk (n.) with a notion of "long, awkward strides," or from O.E. stealcung "a stalking," related to stealc "steep, lofty."