Infantry
Infantry is soldiers trained, armed, and equipped to fight on foot; a branch of an army composed of these soldiers [Merriam-Webster Dictionary].
Word’s origin: 1570s, from French infantry, infanterie (16c.), from older Italian or Spanish infanteria "foot soldiers, a force composed of those too inexperienced or low in rank to be cavalry," a collective noun from infante "foot soldier," originally "a youth," from Latin infantem (see infant). Meaning "infants collectively" is recorded from 1610s. A Middle English (c. 1200) word for "foot-soldiers" was going-folc, literally "going-folk" [Online Etymology Dictionary].
Infantry. Merriam-Webster Dictionary Retrieved from: https://www.merriam-webster.com/dictionary/infantry
Infantry. Online Etymology Dictionary. Retrieved from: https://www.etymonline.com/word/infantry