1. The soldiers or a unit of soldiers who were originally trained to fight on foot: "Traditionally, the young men who were not experienced enough to ride horses in the cavalry joined the infantry."
2. Etymology: from Latin infans, "not speaking" then Italian infante, "youth, foot soldier" and via French infanterie, to English.

The term infantry was first recorded by John Wycliffe in 1382, infant comes from the Latin infans, "unable to speak". It once meant a "childe" or "a young knight, a youth of gentle birth" as well as a baby. So it is that we have the word infantry originally referring to foot soldiers, "soldiers who were too young and too inexperienced to serve in the cavalry".