What do the 3 close horizontal bars (not hamburger menu) represent and what is the origin of the design?

For some reason, those 3 horizontal bars centered in this Jabber client application is something I associate with something you can drag down, but I can't remember at all why I associate 3 bars with something that can be pulled down.

My question is, what do these 3 horizontal bars represent universally, and when did it start doing so? I think I also remember seeing this symbol somewhere on Apple phones but also don't remember where exactly.