'gnat' originates from Old English, specifically the word 'gnætt' (also written 'gnæt'), where it meant 'small biting insect'.

'gnat' changed from Old English 'gnætt' (or 'gnæt') into Middle English forms like 'gnat(e)' and eventually became the modern English word 'gnat'.

Initially, it meant 'small biting insect', and over time this basic sense has remained largely the same; occasionally it has been used figuratively for trivial annoyances.