Piggyback rides?

Why Piggy? Did people ride on the backs of pigs? Or they just say that to me because I’m portly?

From http://m-w.com:
Main Entry: 1pig·gy·back
Pronunciation: 'pi-gE-"bak
Function: adverb
Etymology: alteration of earlier a pick pack, of unknown origin
Date: 1565
1 : up on the back and shoulders
2 : on or as if on the back of another; especially : on a railroad flatcar

The Word Mavins address this.

(The Spelling Mavens took the day off.)

LOL. I caught it after I hit submit - but have never been one to feel the need to correct small errors…