IANAL, but what you should be able to do is have a set of quotes of one or two sentences each from various sources (books, TV, movies, etc.) that have the moder

IANAL, but what you should be able to do is have a set of quotes of one or two sentences each from various sources (books, TV, movies, etc.) that have the modern word or idiom you are specifying. That should then be small enough to fall under fair use (like IMDB, wikiquote, etc. have quotes from films, and good reads, dictionaries, etc. have quotes from books/text), and be plenty enough to capture the meaning of the words/idioms. You could create your own sentences that you control the copyright of containing the word or idiom, as those words and idioms themselves are not copyrightable. For example: "I fracking hate ice cream!" For the rest, there is a lot of text upto 1926 (depending on when the author died) that is available for use, so you only need to capture words and idioms changed since then, including any pop culture terms.