Final answer:
Oxytocin is the hormone that initiates labor by stimulating contractions of the uterus.
Step-by-step explanation:
The hormone that literally means 'swift birth' and initiates labor is oxytocin. During labor, the contractions of the smooth muscles in the uterus are stimulated by the release of oxytocin. This hormone is secreted by the pituitary gland and causes the cervix to stretch, which leads to more forceful contractions and the eventual birth of the baby.