Old English spir "a sprout, shoot, spike, blade, tapering stalk of grass," from Proto-Germanic *spiraz (cognates: Old Norse spira "a stalk, slender tree," Dutch spier "shoot, blade of grass," Middle Low German spir "a small point or top"), from PIE *spei- "sharp point" (see spike, n.1). Meaning "tapering top of a tower or steeple" first recorded 1590s (a sense attested in Middle Low German since late 14c. and also found in the Scandinavian cognates).

early 14c., "send up shoots," from spire, n.. Related: Spired; spiring.