Proto-Indo-European *dʰǵʰem- "earth" with derivatives meaning "earthling" became Proto-Germanic *ǥumōn "man", and then Old English guma "man". This combined with bride to form the Middle English word bridegome, which became bridegroom under the influence of the word groom, an unrelated word meaning "man". The origin of groom is unknown; the word has no other Germanic cognates.
In Greek the o-grade form *dʰǵʰom- became χαμαί khamai "on the ground", which combined with leōn "lion" to form khamaileōn "chameleon". This was borrowed into Latin as chamaeleōn, then into English as chamalioun, chameleon.
The suffixed o-grade form *dʰǵʰom-on- became Latin homō "man", which gives us the words homage and homicide thru Old French. The form *dʰǵʰom-o- became humus "earth", which gives us the words humble, exhume and human, also thru Old French.