The Spanish word 'infantería' (meaning 'infantry') has an interesting etymology that traces back to Latin. It comes from the Latin word 'infans', which literally meant 'not speaking' or 'child', formed from the prefix 'in-' (meaning 'not') and 'for' (meaning 'to speak'). The term evolved through Spanish 'infante' meaning 'foot soldier' and was also influenced by the Italian word 'infanteria' meaning 'foot soldiers'. The connection between 'child' and 'foot soldier' may seem strange at first, but historically, junior soldiers who served on foot (as opposed to mounted cavalry who were typically from the nobility) were called 'infantes'.

Some related Spanish words that might be more familiar to Spanish learners include 'infante' (meaning 'infant' or historically 'foot soldier'), 'infancia' (meaning 'childhood'), and 'infantil' (meaning 'childish' or 'infantile'). All these words share the same Latin root 'infans' and maintain connections to either the original meaning of 'child' or the military meaning that developed later.

English speakers can easily connect 'infantería' to several familiar English words like 'infantry' (the military term), 'infant' (a baby or very young child), and 'infantile' (childish or immature). These English words share the same Latin ancestor 'infans' with the Spanish word. While the English 'infantry' maintained the military meaning like Spanish 'infantería', words like 'infant' kept the original Latin meaning relating to children.