Flip side

What is the meaning and origin of "flip side"? Thanks.

It comes, I believe, from those old-fashioned things (pre-CD, pre-tape, pre-reel-to-reel, and pre-8-track tape) called records -- used to be played on record players. The disks have two sides -- on a 45 RPM disk, sides A & B. The song that the record company wanted to promote most heavily would go on the A side. So when a DJ played that side, he'd (they were always "he" back then) sometimes say, "And now on the flip side...", and play side B, the lesser known track.

Oh, Lord, I'm getting old.

Me, too. Oy. There is another use of flip side, derived from the gone-and-best-forgotten CB radio fad of the '70s, (Do they still exist?) Long-distance truckers, and trucker wannabes, speaking from truck-to-truck. "Catch you on the flip side" was CB slang for "I'll contact you on the return trip" ... the metaphor of a record turning being applied to you trip from Point B back to A.