What does it mean to be jealous at night and borrow some crabs?

This was originally a little joke, and it probably meant something like this:

One night, a family ate crabs. Because there was no vinegar at home, he asked his son to borrow it from his neighbor's house. The child took a bowl and borrowed a bowl of vinegar from the door. But this neighbor is very narrow-minded and greedy.

After a while, the neighbor also asked his son to bring a bowl for home. His son said, my family is jealous today, lend us some crabs to eat. ....

There is irony here.

Come to think of it, I want to get married and borrow a daughter-in-law