From a Late Old English (11th century) word dubban perhaps borrowed from Old French aduber, adober (also 11th century, Modern French adouber), from Frankish *dubbjan, from Proto-Germanic *dubjaną ("to fit"), from Proto-Indo-European *dʰewbʰ- ("plug, peg, wedge").
Cognate with Icelandic dubba (dubba til riddara). Compare also drub for an English reflex of the Germanic word.