- lactation
- 1668, "process of suckling an infant," from Fr. lactation, from L. lactationem (nom. lactatio) "a suckling," from L. lactatus, pp. of lactare "suckle," from lac (gen. lactis) "milk," from PIE base *glact- (cf. Gk. gala, gen. galaktos "milk"). Meaning "process of secreting milk from the breasts" first recorded 1857; lactate (v.) in this sense is a back-formation from 1889. Lactic acid is from 1790; so called because it was obtained from sour milk. M.Ir. lacht, Welsh llaeth "milk" are loan words from Latin.