Cfb51 Linguistics time:
In the past, this board has sometimes grumbled about the conventional use of BYE versus IDLE in football. I think it had something to do with the fact that "bye" games, as originally applied to sports, indicated tournament rounds that a high ranking team had earned the right to skip. The conference basketball tournament is a good example of that use. Obviously that's not what we mean in football. And I recall this other use grating on some posters.
Of course, the way we use words (a society's frequency of word use) is the thing that most directly sets our definitions. Not origins and etymology. It's the same reason Merriam-Webster now treats "figuratively" as an accepted definition of "literally." Because what was formerly called the "incorrect use" was found so frequently that our language philosophies require redefining it as a new correct use. Every language does this incessantly. It's a main driver of how languages evolve.
As it applies to Bye/Idle and sports, it seems Bye has acquired both definitions and that Idle is seldom used at all.