oxytocin

Concise Oxford English Dictionary © 2008 Oxford University Press:
oxytocin /ˌɒksɪˈtəʊsɪn/

▶noun Biochemistry a hormone released by the pituitary gland that in women causes increased contraction of the womb during labour and stimulates the ejection of milk into the ducts of the breasts.

– origin 1920s: from Gk oxutokia ‘sudden delivery’ (from oxus ‘sharp’ + tokos ‘childbirth’) + -in1.