Invented in the latter half of the twentieth century. It can be explained as a short form ofLetitia orVenetia, or fromEstonianTiia, pet form ofDorothea.
Tia
FromMiddle High Germantür, fromOld High Germanturi, fromProto-West Germanic*dur, fromProto-Germanic*durz, fromProto-Indo-European*dʰwer-.