'traditionally-kept' originates from the combination of 'traditionally' and 'kept', where 'traditionally' comes from 'tradition', meaning 'customs or beliefs passed down', and 'kept' is the past participle of 'keep', meaning 'to maintain or preserve'.

'traditionally-kept' evolved from the phrase 'traditionally kept', which was used to describe things maintained according to tradition.

Initially, it meant 'maintained according to tradition', and this meaning has largely remained the same in modern usage.