It's different, and kind of cool, but it does remind me of the word Tertiary.
I've never seen this name before. I think I may prefer it written than how it actually sounds out loud though...TURR-sha.
The name
Trista has been on my mind lately, which I think has a similar feel, but I fear too many people would be confounded by it and mispronounce it as
Trisha.
Tristan on a girl might be cool, like a variant of
Kristen, but I usually don't like the idea of stealing established boys names to use on girls (since society has a terrible problem of teasing boys who have unisex name as having a girl's name).