'hair' originates from Old English, specifically the word 'hær', where the root meant 'hair, covering of the head or body'.

'hair' changed from Old English 'hær' to Middle English forms such as 'hare'/'her' and eventually became the modern English word 'hair'.

Initially, it referred generally to 'hair' or 'a covering of hairs' on the body; over time it maintained that core meaning but also came to be used specifically for head hair and figurative expressions.