before vowels mast-, word-forming element meaning "female breast, mammary gland," from Greek mastos "woman's breast," from madan "to be wet, to flow," from PIE *mad- "wet, moist, dripping" (source also of Latin madere "be moist;" Albanian mend "suckle;" see mast (n.2)).
Entries linking to masto-
mast n.2
"fallen nuts or acorns serving as food for animals." Old English mæst, the collective name for the fruit of the beech, oak, chestnut, and other forest trees, especially serving as food for swine, from Proto-Germanic *masto (source also of Dutch, Old High German, German mast "mast;" Old English verb mæsten "to fatten, feed"), perhaps from PIE *mad-sta-, from root *mad- "moist, wet," also used of various qualities of food (source also of Sanskrit madati "it bubbles, gladdens," medah "fat, marrow;" Latin madere "be sodden, be drunk;" Middle Persian mast "drunk;" Old English mete "food," Old High German muos "meal, mush-like food," Gothic mats "food").
amastia n.
"complete failure of one or both breasts, including the nipple, to develop," 1878, medical Latin, from German amastia (1841), from Greek amastos "without breasts," from privative prefix a- "not, without" (see a- (3)) + mastos "breast" (see masto-) + abstract noun ending -ia.