THANK YOU for posting this song. You’d think that after padding around this planet as a Christian all these years that I would have bumped into this marvelous song, but I had not until you came to my rescue!!!
The "men" word in the title used to indicate all Christians, females also. But these days, our men really need our encouragement to learn the talk and walk the walk, so...
If one were to adapt it for general male and female caroling, it might be sung, "Good Christians all rejoice..."
It is a German and Latin carol from the Middle Ages, whose former title was In Dulci Jubilo. Here is a lovely rendition of that ancient version.