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.