/rɪər/
[noun] The back part of something, or the area behind a person, group, or object. It can also refer to the part of an army that is furthest from the fighting at the front.
'Rear' is a military word in disguise — it came from a battle formation, not a body part.
The word 'rear' arrived in English during the 13th century, carried in by the French-speaking Normans who had ruled England since 1066. It came from Old French 'rere', meaning 'behind' or 'at the back', which itself descended from the Latin adverb 'retro', meaning 'backwards' or 'behind'. That Latin root also gives us the prefix 'retro-' that appears in words like 'retrograde' and 'retrospect', connecting our humble word to a surprisingly large family.
In its earliest English life, 'rear' was almost entirely a military term. Medieval armies were organised into formations, and the portion of troops positioned at the back — away from the enemy — was called the 'rear guard', from Old French 'rereguarde', meaning 'back guard'. This phrase survives today as 'rearguard', and the military sense of 'rear' as the back section of an army or fleet remained its dominant meaning for several centuries. Soldiers understood instantly what it meant to 'protect the rear' or to be stationed 'at the rear'.
Over time, the word shed its exclusively military coat and spread into everyday use. By the 16th and 17th centuries, English speakers were using 'rear' to describe the back of any object, building, or procession — not just an army. The 'rear' of a house was its back side; the 'rear' of a crowd was the people at the end. This widening of meaning is a common pattern in English, where words from specialised professional or military contexts gradually become part of general speech as the culture that created them changes.
Interestingly, the Latin root 'retro' also fed into Old French as 'arriere', meaning 'behind' or 'backwards', which English borrowed separately as 'arrear' — the state of being behind in a payment or duty. The plural 'arrears' is still used today when someone owes money they have not yet paid. So 'rear' and 'arrears' are quiet cousins, both tracing their ancestry back to the same Latin 'retro', though they arrived in English through slightly different Old French paths.
The informal use of 'rear' to mean the buttocks developed later, emerging as a polite or humorous euphemism — a way of referring to the body's back side without using more direct language. This sense follows a predictable logic: the rear is simply the back part of a person, just as it is the back part of anything else. This gentle, indirect usage has been common in English for at least two centuries, showing how a word's journey never quite ends — it keeps collecting new meanings as each generation finds new uses for it.