Etymology
From Middle English *spene, *spane, from Old English spane, spanu (“teat”), from Proto-West Germanic *spanu, *spenu, from Proto-Germanic *spenô (“nipple”), from Proto-Indo-European *pstḗn (“breast; teat”). Cognate with West Frisian spien (“nipple”), Dutch speen (“nipple”), Danish spene (“teat”), Swedish spene (“teat, nipple, dug”), Icelandic speni (“teat”).
Alternatively a borrowing from Dutch speen (“nipple, teat”), from the same Proto-Germanic origin as above.