Thetis was a minor Greek goddess,
Achilles' mother in
Homer's
Iliad, so it's likely that's where the name comes from. The fact that Thetis is a sea nymph makes
Marine a little redundant as a MN, though. It's prn Thet-iss (short E, soft S)
Wit has truth in it; wisecracking is simply calisthenics with words.