"the first milk secreted in the breasts after childbirth," 1570s, from Latin colostrum "first milk from an animal," earlier colustra, a word of unknown etymology.
It forms all or part of: ablactation; cafe au lait; galactic; galaxy; lactate (v.); lactate (n.); lactation; lacteal; lactescence; lactic; lactivorous; lacto-; lactose; latte; lettuce.
It is the hypothetical source of/evidence for its existence is provided by: Latin lac (genitive lactis) "milk;" Greek gala (genitive galaktos), "milk;" Armenian dialectal kaxc' "milk." The initial "g" probably was lost in Latin by dissimilation. This and the separate root *melg-, account for words for "milk" in most of the Indo-European languages. The absence of a common word for it is considered a mystery.
1570s (adj.), "draining out;" 1610s (n.), in anatomy, "an emulgent vessel," from Latin emulgentem (nominative emulgens), present participle of emulgere "to milk out, drain out, exhaust," from assimilated form of ex "out" (see ex-) + mulgere "to milk" (from PIE root *melg- "to rub off; to milk"). Related: Emulgence.
1660s, "process of suckling an infant," from French lactation, from Late Latin lactationem (nominative lactatio) "a suckling," noun of action from past-participle stem of lactare "to suckle," from lac (genitive lactis) "milk" (from PIE root *g(a)lag- "milk"). Meaning "process of secreting milk from the breasts" first recorded 1857. Related: Lactational.
early 15c., "draw off (humors or spirits) as vapor," from Late Latin evaporatum, past participle of evaporare "disperse in vapor" (see evaporation). Intransitive sense by 1560s. Figurative use by 1610s. Related: Evaporated; evaporating. Evaporated milk (1870) is processed milk with some of the liquid removed by evaporation; it differs from condensed milk in being unsweetened.