I don't know if I will be able to answer your question completely, but I'll take a stab at it.

I did some research and found everything from children questioning these statements to references of Marlon Brando playing Stanley in A Streetcar Named Desire.

What does seem to be consistent is the type of clothing.  The question about the tank top seems to have evolved from a student in a private school wanting to know why the school would object to it.  There is a very fine line between tank tops and spaghetti strap shirts. 

However, making the jump from that phrase to a wife beater seems to have proved the most difficult in the research.  Some of the discussions I read seem to think it might be racially motivated.  These racial indications stem anywhere from African-American to Italian to the back hills of the United States.

Since I really couldn't find a definitive answer, I would be guessing when I say another definition of the garment you are asking about would be a "muscle shirt" because the T-shirt in question exposes all the muscles a person has in their upper arms as well as the chest and addomen muscles can sometimes be seen.  A man beating his wife would, I would presume, use his muscles. 

That would be my guess, but I am really not sure.

Merry Meet and Merry Bide

Cheryl