As was pointed out by JDK in the comments of another question, all of the 95 questions tagged asio deal directly with boost-asio. 52 of which, are tagged with both. Of which, only 37 of which are tagged with boost, also. This implies that there are 37 tags tagged with boost and asio, but not boost-asio, although that is the clear intent. This seems a natural case for a synonym.