spheno-

Old English spon "chip, sliver, shaving, splinter of wood," from Proto-Germanic *spe-nu- (source also of Old Norse spann, sponn "chip, splinter," Swedish spån "a wooden spoon," Old Frisian spon, Middle Dutch spaen, Dutch spaan, Old High German span, German Span "chip, splinter"), from PIE *spe- (2) "long, flat piece of wood" (source also of Greek spathe "spade," also possibly Greek sphen "wedge").

As the word for a type of eating utensil, c. 1300 in English (in Old English such a thing might be a metesticca), in this sense supposed to be from Old Norse sponn, which meant "spoon" as well as "chip, tile." The "eating utensil" sense is specific to Middle English and Scandinavian, though Middle Low German spon also meant "wooden spatula." To be born with a silver spoon in one's mouth is from at least 1719 (Goldsmith, 1765, has: "one man is born with a silver spoon in his mouth, and another with a wooden ladle").

1732, from spheno- + -oid. As a noun from 1828. Related: Sphenoidal.