deltoid (adj.)

c. 1200, name of the fourth letter of the Greek alphabet (equivalent to our D), which was shaped like a triangle. The name is from Phoenician daleth "tent door." Sense of "triangular island or alluvial tract between the diverging branches of the mouth of a great river" is because Herodotus used it of the delta-shaped mouth of the Nile. It was so used in English from 1550s and applied to other river mouths, of whatever shape, by 1790. Related: Deltaic; deltification.

"deltoid muscle," short for deltoid (q.v.). Related: Delts.

word-forming element meaning "like, like that of, thing like a ______," from Latinized form of Greek -oeidēs (three syllables), from eidos "form," related to idein "to see," eidenai "to know;" literally "to see" (from PIE *weid-es-, from root *weid- "to see"). The -o- is connective or a stem vowel from the previous element. Often implying an incomplete or imperfect resemblance to the thing indicated.