Multiple letters together can be read as a multiple of the single letter. "TT" can be tease, as can TTT and TTTT! "CC" can be seize (or to seize), etc.
Before you order a vanity plate, test it out on a few people. Unless you're ready to explain it to everyone you meet, make it at least possible to decypher! I got pretty tired of explaining CC DDAY to people. (A la carpe diem.)
You can also consider using a license plate frame to further explain the plate to curious parties.
BTW, The most popular personalized plate requested on the first day of seven letter plates in California was *PORSCHE*