A person, usually a male, who is unknowingly entering into a relationship where the “significant other” will very slowly begin to try to control him/her, change him/her, and nag him/her, but the level of control rises ever so slowly so the other person (the “frog”) doesn’t even realize what is taking place, until it is too late. Now he/she is so far into the relationship that it is very difficult to extract oneself from it. A break-up at this point is often difficult and rich in drama, for by the time the individual realizes he/she is miserable in the relationship and wants out, the couple is already living together, commingling assets, or may have made significant purchases together (e.g. real estate). Frequently the female may have intentionally become pregnant by lying about the use of birth control or the ability to even get pregnant as an attempt to keep the male in the relationship, or at the very least, assure annuity payments for herself from him for the next 18 years.
The euphemism compares you to a frog in the following scenario: You put a frog into a pot of cold water. The frog is happy, splashing around in the pot, and having a grand time. You put the pot on the stove and turn on the burner on a low setting. The frog is still happy, swimming around, and content. He may not even notice the water becoming warmer. Maybe the slight warmth feels good. Now you turn up the heat. The water temperature rises, but it’s very slow, and so gradual that the frog doesn’t even notice. It’s kind of like watching a clock. The hands are moving, but it’s so slow, you don’t notice. But the heat is still being applied. The frog doesn’t realize what’s happening until it’s too late to escape. Now he’s frog soup. And this could be you. You’re frog soup.
What??? She’s pressuring you to let her move in with you? You just started dating her! Are you crazy? Don’t you see what’s happening here? Dude…..you’re frog soup!