from The American Heritage® Dictionary of the English Language, 4th Edition
- interj. Used to command a horse to go ahead or go at a faster pace.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- interj. Move on!, go faster! (Derived from 'Get Ye Up' or 'Git Thee Up')
Alteration of get up.(American Heritage® Dictionary of the English Language, Fourth Edition)