spur: [OE] Spur goes back ultimately to Indo- European *sper- ‘hit with the foot, kick’ (source also of English spurn [OE], which originally meant literally ‘hit with the foot, trip over’). From it was descended the prehistoric Germanic noun *spuron, which produced German sporn ‘spur’, Dutch spoor ‘track’ (source of English spoor [19]), and Swedish sporre ‘spur’ as well as English spur. => spoor, spurn
spur (n.)
Old English spura, spora "metal implement worn on the heel to goad a horse" (related to spurnan "to kick"), from Proto-Germanic *spuron (cognates: Old Norse spori, Middle Dutch spore, Dutch spoor, Old High German sporo, German Sporn "spur"), from PIE *spere- "ankle" (see spurn). Related to Dutch spoor, Old English spor "track, footprint, trace."
Generalized sense of "anything that urges on, stimulus," is from late 14c. As a sharp projection on the leg of a cock, from 1540s. Meaning "a ridge projecting off a mountain mass" is recorded from 1650s. Of railway lines from 1837. "Widely extended senses ... are characteristic of a horsey race" [Weekley]. Expression on the spur of the moment (1801) preserves archaic phrase on the spur "in great haste" (1520s). To win one's spurs is to gain knighthood by some valorous act, gilded spurs being the distinctive mark of a knight.
spur (v.)
c. 1200, from spur (n.). Figurative use from c. 1500. Related: Spurred; spurring. Old English had spyrian, but it meant "follow the track of, track down, investigate."