Bree history
 

I'm sure I read somewhere in either UT or LotR that Bree once had a different name (perhaps when Arnor was still extant). Did I dream it or does anyone here know what it was?

I can't find anthing about another name for Bree, not in the indices of LotR and UT, nor in my reference book or on the Encyclopedia of Arda.

Bree never had another name. Perhaps you are thinking of its True Westron name, of which Bree is just a translation (cf. Appendix F). However, not even taht name is to be found in the books.