lactation (n.)

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.