Seen in Strong Bad Is In Jail Cartoon, this is cleverly? hidden in Strong Mad's cake to help his brother and his buddy escape... after they're freed.

Jack Hamma is reffered to Jeff Hannah, a character played by Adam Baldwin in the movie called [3:15] (which is banned in Finland, Sweden and Iceland). -Maudi Algabban

See [3:15] at the IMDB

Actually, I think it's a reference to "Jack Hannah", the famed 'animal guy' of many a late night talk show. - Shalimar Bojangles

It's always possible that it is called Jack Hamma because it is a Jack Hammer and Strong Mad can't spell