What does in mean in the following sentence?
MTV Europe Music Awards nominations are in and Lady Gaga leads
It feels like "announced", but does it refer to "in the news" or something? Where does it come from?
This sense of in means
Your example, nominations are in and Lady Gaga leads, makes it clear that the nominations have not merely been sent in, but already received by the judges, read, and tallied. However, sometimes a phrase like this refers more to the time of submission, implying that the item will also be received at that time, but might not be handled until later. For example:
This use of in often relates to judging—note the words like nominations and votes—but you might use it when referring to anything that is sent or submitted.
The in in the sentence refers to the nominations having been submitted and appropriately received. We know they were received because there is an official tally in which Lady Gaga leads.
Etymologically, using the preposition in likely refers to a long-standing tradition among organizations to convene nominating people and things for awards, elections, and whatever by having those empowered to nominate submit their nominations by putting them in a hopper. When nominations are in the hopper, they are in. Colloquially and idiomatically, the preposition in is still used even if there is no hopper.