"A hormone released by the pituitary gland that causes increased contraction of the womb during labour and stimulates the ejection of milk into the ducts of the breasts", 1920s: from Greek oxutokia 'sudden delivery' (from oxus 'sharp' + tokos 'childbirth') + -in1.[oxytocin etymology, oxytocin origin, 英语词源]
"The main part of the neurohypophysis (the posterior lobe of the pituitary gland)", Early 20th century. From classical Latin parspart + nervōsa, feminine of nervōsus.