'Not' is a worn-down form of 'nought' (no thing) — it replaced the original Old English negator 'ne.'
Used to form the negative of a verb or to deny, refuse, or contradict something.
From Middle English 'not,' contracted from 'noht, nought,' from Old English 'nāwiht, nōwiht' (nothing, not), a compound of 'nā' (no, never) + 'wiht' (thing, creature). Literally 'no thing, nothing.' Old English negated verbs with 'ne' alone ('ic ne wāt' — I don't know), but a reinforcing 'nāwiht' was added for emphasis. Eventually the original 'ne' was dropped and the reinforcing 'nought' — worn down to 'not' — became the sole negator. This is called Jespersen's Cycle, a pattern seen in French
'Not' literally means 'no thing.' It followed the same path as French 'ne...pas,' where 'pas' (a step) was added for emphasis ('I don't walk a step') and eventually replaced the original negator 'ne.' In English, 'nought' (no thing) reinforced 'ne,' then replaced it. Linguists call this Jespersen's Cycle — negators weaken, get reinforced, and the reinforcement becomes the new negator.