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.
German and Jewish (Ashkenazic): from Middle High German wīn, German Wein ‘wine’, hence a metonymic occupational name for a wine merchant or producer, or perhaps for a tavern keeper. As a Jewish name it may also be of ornamental origin.