Why is the ninth month called September?
Old English spere, from Proto-Germanic *speri (cf. Old Norse spjör, Old Saxon, Old Frisian sper, Dutch speer, Old High German sper, German Speer "spear"), from PIE root *sper- "spear, pole" (cf. Old Norse sparri "spar, rafter," and perhaps also Latin sparus "hunting spear").
"sprout of a plant," 1540s, variant of spire.
1755, from spear (n.1). Related: Speared; spearing.