Old English hoc "hook, angle," perhaps related to Old English haca "bolt," from Proto-Germanic *hokaz/*hakan- (cf. Old Frisian hok, Middle Dutch hoek, Dutch haak, German Haken "hook"), from PIE *keg- "hook, tooth" (cf. Russian kogot "claw"). For spelling, see hood (n.1).
Boxing sense of "short, swinging blow with the elbow bent" is from 1898. Figurative sense was in Middle English (see hooker). By hook or by crook (late 14c.) probably alludes to tools of professional thieves. Hook, line, and sinker "completely" is 1838, a metaphor from angling.
To “fall for something hook, line, and sinker” is to be fooled completely. “Tom doubted that his ruse would fool anybody, but the boss fell for it hook, line, and sinker.” The reference is to fishing tackle.
Totally; completely: she's got you hook, line, and sinker