Infant \in-FENT\ , noun;
1. Baby, or child younger than 1 year old
This word dates to the late 14th century and originally applied to a wider range of ages, sometimes as old as 7. It comes from Latin infantem ("young child, babe in arms") which was the noun usage of an adjective meaning "unable to speak" from in- + fans ("not" + "speak").
Thanks Inky Fool!