infant XIV. ME. enfaunt (with early assim. to L.) — (O)F. enfant :- L. infāns, -ant-, sb. use of infāns unable to speak, f. IN-2 + prp. of fārī speak; see FAME, -ANT.
So infancy XV. — L. infantia. infantile XVII. — F. or L. infantry XVI. — F. infanterie — It. infanteria, f. infante youth, foot-soldier.

in·fant / ˈinfənt/ • n. a very young child or baby. ∎  [as adj.] denoting something in an early stage of its development: the infant science of bioelectrical medicine. ∎ Law a person who has not attained legal majority.

infant (in-fănt) n. a child incapable of any form of independence from its mother: usually, a child under one year of age, especially a newborn child. i. mortality rate the number of deaths of children under one year of age per 1000 live births in a given year. Included are the neonatal mortality rate (calculated from deaths occurring in the first four weeks of life) and postneonatal mortality rate (from deaths in the remainder of the first year).