Honestly, cis- was new to me. The first time I remember encountering it, in fact, was with the term cisgender. But trans? I mean, trans- is everywhere. Transnational, transformer, the Transcontinental Railroad, etc. A lot of Texans object to the Trans-Texas Corridor, but no one complains about being confused by the name. It's common in corporate names, as well: Transunion, Transamerica...