The only place I've seen this song is in the John F. Feierabend collection - The Book of Bounces.

Hop, chop, my little horse
Hop, chop again
How many miles to Dublin?
Three score and ten.
Whill I be there by candlelight/
Yes sir, and back again.
So hop, chop my little horse.
Hop, chop again.

Now, I happen to know almost nothing about horses. I fell off one when I was little - that's about the sum of my experience. So could anyone please explain to me what "chop" means in this song?

Thanks.

~b.w.