xxx's and ooo's

My granddaughter asked me why, in a letter she received, the xxx’s and ooo’s at the bottom stood for hugs and kisses. I couldn’t find the answer. Anybody out there have any idea how or why this got started? Thanks…

This should be helpful:

I don’t know how I managed to mess up in posting that link, but I’ll try again.

You’re awesome!

That link straightened me out. My fourth grade teacher explained it to us as the “X” being hugs, like it was arms crossing in a hug. The “O” was a kiss because it looked like lips.