What does jus primae noctis mean in the book 1984?
At least legally, it is said that medieval lords had the right to sleep with any woman on their lands on her wedding night. In other words, when one of "their" people got married, they had the right to have her sleep with them, not their husbands, on the first night. We do not know for sure that this really happened.
In 1984, we see this referred to as one of the ways in which things were terrible before the revolution. Winston knows that, supposedly, capitalists had this right (this is in Chapter 7). However, according to Party propaganda, the right was not limited to the wedding night. Instead:
It was the law by which every capitalist had the right to sleep with any woman working in one of his factories.