A very popular name, of uncertain derivation. Until the 20th century it was confined mainly to Scotland and Ireland. It is probably of Scandinavian rather than Celtic origin, however: a short form of any of the various compound names derived from Old Norse brand ‘sword’. Its popularity in Gaelic-speaking countries has no doubt been influenced by its similarity to Brendan.
English: habitational name from a place in Berkshire named Wadley, from Old English wād ‘woad’ or the personal name Wada + lēah ‘woodland clearing’. Wadley in Northumberland, which has the same derivation, appears not to have contributed significantly to the modern surname.