"large nail," mid-14c., perhaps from Old Norse spik "splinter" (related to Old English spicing "large nail"), from Proto-Germanic *spikaz (cf. Middle Dutch spicher, Dutch spijker "nail," Old English spaca, Old High German speihha "spoke"), from PIE root *spei- "sharp point" (cf. Latin spica "ear of corn," spina "thorn, prickle, backbone," and perhaps pinna "pin" (see pin (n.)); Greek spilas "rock, cliff;" Lettish spile "wooden fork;" Lithuanian speigliai "thorns," spitna "tongue of a buckle," Old English spitu "spit").
But based on gender difficulties in the Germanic words, OED casts doubt on this whole derivation and says the English word may be a borrowing of Latin spica (see spike (n.2)), from the same root. Slang meaning "needle" is from 1923. Meaning "pointed stud in athletic shoes" is from 1832. Electrical sense of "pulse of short duration" is from 1935.
