Once upon a time, a long time ago newspapers were made of thin, low-cost, non-archival paper called newsprint and they were divided into sections. One section, the Classifieds (also known as the want ads because you could find anything you wanted there) contained short advertisements, classified (hence the name) by categories.
Want to find something you lost? Check out the want ads. Want to find a job, a roommate or a place to live? Check out the want ads. What to find the man of your dreams or a puppy? Check out the want ads.