'avail' originates from Old French (anglicized forms from Anglo-Norman) specifically the word 'availer' or 'avail', ultimately from Latin-related roots where 'valēre' meant 'to be strong, to be worth'.

'avail' changed from Anglo-Norman/Old French words such as 'availer'/'availlier' and eventually became the modern English word 'avail' and its forms like 'availed' through Middle English usage.

Initially, it meant 'to be strong or have worth' (from Latin 'valēre'), but over time it evolved into the sense 'to be of use, to help, or to make use of' as in modern English.