Where does the term "sex kick" come from?

Solution 1:

There was a Reddit thread some years back where the community discussed this, and the most-upvoted explanation given was:

In sex, the thrust is presumably the strongest. That is why a sex kick is stronger during the first few frames.

A reverse sex kick (Dr Mario) is basically just saying that the man with a PHD prefers to go hard after the thrust.

It's a bit weak as far as innuendo goes, but I'd guess at least part of the name choice probably has to do with it being a game that was incredibly popular with teenage boys rather than any inherent property of the moves.