'13' originates from Old English, specifically the word 'þrēotīene', where 'þrēo' meant 'three' and 'tīene' meant 'ten'.

'þrēotīene' transformed into the Middle English word 'thrittene', and eventually became the modern English word 'thirteen'.

Initially, it meant 'three plus ten', and this meaning has largely remained the same in modern usage.