groom: [13] No one has ever been able satisfactorily to explain where the word groom came from. It suddenly appears in early Middle English, meaning ‘boy, male servant’ (the sense ‘one who takes care of horses’ is a 17th-century development), and none of the words with a superficial similarity to it, such as Old French grommet ‘servant’ and Old Norse grómr ‘man’, can be shown to be related. Bridegroom is a 14th-century alteration of Old English brydguma (the element guma ‘man’ is related to Latin homō ‘man’) under the influence of groom. [groom etymology, groom origin, 英语词源]