How can I partition a set of words given pairs that must end up together?

I have a space or comma separated table with two columns, each row representing equivalence of the two words. A B B C B D C E F G What I want is a table with each row listing all mutually equivalent words. A B C D E F G That is if two words ever occur on the same row of input they must end up in the same row of the output. Any tool would do.