Comment by SomethinGirlygamer on Unfavored Courtier - Chapter 19 : the unexpected arrival of..

Lope is indeed a gait of a horse, it's like a slow canter. That being said, I have never used it as a verbal command, nor heard anyone else (though it's not impossible). I think it's supposed to be used like a giddy-up here. Most people just use a percussive sound, like Hup, Hyah, and a loud click.