[1] Similarly, according to Adler, in the Ambrosian Lexicon. (On stoikheion "letter", see eta 614.) The letter delta and its name were borrowed from the Semitic daleth (Hebrew ד) to represent a voiced dental stop. The shape of the letter allowed it to be applied to various triangular entities, such as the delta of a river, the constellation Triangle, and -- see further, next note -- the female pubic triangle. LSJ entry at web address 1.
[2] Aristophanes Lysistrata 151 (text at web address 2). See the commentary by J. Henderson (Oxford 1987), p.85, slightly modifying his earlier remarks in The Maculate Muse (New Haven 1975) 146.