'toluidine' originates from 'toluene', specifically the word 'toluidine', where 'tol-' referred to 'toluene' and '-idine' is a chemical suffix indicating a derivative.

'toluidine' changed from 'toluene' word 'toluidine' and eventually became the modern English word 'toluidine'.

Initially, it meant 'a derivative of toluene', and this meaning has largely remained the same in modern usage.