I
love Tiamat. Even though it's been a favorite of mine for sometime, I doubt I'd ever use it (but who knows?). Still, I think it's fantastic, for child or cat.
Thekla, I'm not so sure about. Inexplicably, it brings to mind cleaning products and ceramic floors. It just doesn't sound like a name to me, you know? If I heard it out in the real world without any former knowledge of it, I'd probably go, "WTF?" Not a bad meaning though.