Origins
The English word 'infantry' entered the language around 1579 from French 'infanterie,' which was borrowed from Italian 'infanteria,' the collective term for foot soldiers. The Italian word derives from 'infante,' which in medieval usage meant a youth, a servant, or a foot soldier. 'Infante' itself comes from Latin 'infāns, infantis,' meaning one who does not speak, a child — composed of the negative prefix 'in-' and 'fāns,' the present participle of 'fārī' (to speak). The PIE root is *bʰeh₂- (to speak), which also produced Greek 'phēmí' (I say), giving English 'fame,' 'fable,' 'fate,' and 'prophet.'
The semantic journey from 'speechless child' to 'foot soldier' is one of the most remarkable in military vocabulary. In the Roman period, 'infāns' meant simply a very young child, one who had not yet learned to speak. By the medieval period in Italy, 'infante' had broadened to mean a youth or a young person of noble birth, particularly one who had not yet been knighted. Since knighthood entitled a young nobleman to fight on horseback, those who had not yet earned this status fought on foot. They were the 'infanti' — the young ones, the juniors — and their collective body was the 'infanteria.' The social hierarchy of medieval warfare thus inscribed itself into the vocabulary: cavalry were knights, nobility; infantry were youth, the unproven.
The Spanish royal title 'Infanta' (for a princess) and 'Infante' (for a prince who is not heir to the throne) preserves the older noble meaning of the word. A Spanish Infanta and an infantry soldier share the same etymological root: both are 'the young ones.' The Portuguese royal family used the same titles. This connection — between royal children and common foot soldiers — captures the feudal world's complex relationship between nobility and military service.
Old English Period
Infantry has been the backbone of armies since organized warfare began. Before the word existed, the concept was universal: foot soldiers formed the mass of every army from the Sumerian phalanx to the Roman legions to the English longbowmen at Crecy. The Greek 'hoplite,' the Roman 'miles,' the Anglo-Saxon 'fyrd' — all were infantry under different names. The Italian-derived word 'infantry' became the international standard because Italian military theory and practice dominated European warfare in the fifteenth and sixteenth centuries.
The relationship between infantry and cavalry has structured military thinking for millennia. In the medieval period, cavalry — mounted knights — was considered the superior, aristocratic arm. Infantry was for commoners, mercenaries, and those too poor or too young for horses. This class distinction persisted long after the tactical reality changed: by the late Middle Ages, disciplined infantry formations (Swiss pikemen, English longbowmen) could reliably defeat cavalry charges. Yet the vocabulary preserved the hierarchy: cavalry from 'cavaliere' (gentleman, horseman); infantry from 'infante' (youth, the junior).
The compound 'infantryman' appeared in the seventeenth century. 'Infantry' can function both as a collective noun (the infantry advanced) and as a modifier (an infantry regiment). The abbreviation 'Inf.' is standard in military writing. 'Light infantry,' 'heavy infantry,' 'mechanized infantry,' and 'motorized infantry' describe different types distinguished by their equipment and mobility — though a 'mechanized infantryman' who fights from an armored vehicle is etymologically a 'child in a machine,' which captures the absurd beauty of linguistic evolution.
Modern Usage
Despite the advent of tanks, aircraft, missiles, and drones, infantry remains central to military doctrine. The principle that territory is not truly controlled until a soldier stands on it with a rifle has proven remarkably durable. Modern infantry bears little resemblance to the medieval 'infanti' who gave them their name — today's foot soldiers carry advanced weapons, communications equipment, night vision, and body armor — but the core function is the same: the human being on the ground, fighting on foot.
The word's connection to 'infant' has generated occasional dark humor among soldiers. Infantrymen have long been aware that their branch name derives from a word for children, and the irony is not lost on those who bear the heaviest combat burden. In English-speaking armies, the phrase 'Poor Bloody Infantry' (PBI) has been used since World War I to describe the foot soldier's lot with weary affection.