1847, a back-formation from gestation. Related: Gestated; gestating.

"action or process of carrying young in the womb," 1610s, earlier (1530s) "riding on horseback, etc., as a form of exercise," from Latin gestationem (nominative gestatio) "a carrying," noun of action from past-participle stem of gestare "bear, carry, gestate," frequentative of gerere (past participle gestus) "to bear, carry, bring forth" (see gest). Meaning "action or process of carrying young in the womb" is from 1610s.