Probably from good man, but compare also Anglo-Saxon gumman a man, Old High German gomman man, husband.
"goman." YourDictionary, n.d. Web. 23 June 2018. <http://www.yourdictionary.com/goman>.
goman. (n.d.). Retrieved June 23rd, 2018, from http://www.yourdictionary.com/goman
Do you use YourDictionary every day? If not, remember that it is never to late to do so!
Let us be there for you: