The spelling of 'goodbye,' which is now standard, also varied in earlier centuries, so it's not surprising that some older sources might have a spelling that's now strictly speaking a mistake.
As for Urban Dictionary, some things in it are accurate, but many are just someone's guess that sounds plausible to a few other people who also have no clue. IMO this is in the latter group. You can choose to believe the dubious 'explanation' if you want to, but it will still be an eggcorn -- a mistake that people explain to themselves by drawing a false etymological connection. The discussion explains why people think it might be right to change the spelling, but it doesn't make it clear that it isn't right. So you could even do UrbanDict a favor by registering a thumbs-down, and not quoting it.
But anyway, I'm glad you found the other background helpful. When songs are sung by so many people, it's good to know which versions are more faithful to the original. I'm pretty sure Willie Nelson wouldn't have sung 'be' instead of 'meet,' for example, but it would be nice if people who put clips on YouTube would take as much care as the artists to get the details right.