It means 'good luck'. We all want as much of it as we can get. So it is not surprising that it became a proper noun, the name of some people, a tribe of Israel, and a god. The god Gad was not ordinarily identified with Baal. But the identities of ancient Mediterranean gods were quite fluid, so it wouldn't be surprising if the two deities were identified with each other somewhere at some time.
Human languages are full of such interesting but meaningless coincidences.
The development that prompts this little lesson in Hebrew and linguistics today is a silliness attack among some within the Holy Name movement. I am not criticizing the majority of the people who accept some version of the Holy Name theology. For the most part, I think, they are sincere people who love God, and are not afraid to break tradition and think for themselves. Much as I may disagree with their opinions, I agree with them . His Holy four-letter Name.