'accidence' originates from Latin, specifically the word 'accidentia,' where 'accident-' meant 'happening' or 'event.'

'accidentia' transformed into the Old French word 'accidence,' and eventually became the modern English word 'accidence' through Middle English.

Initially, it meant 'a happening or event,' but over time it evolved into its current meaning of 'the part of grammar dealing with inflections.'