What's the meaning of the phrase 'Gee-up'?
'Gee-up' is a command given to a horse, usually to encourage it to go forward or go faster.
To gee things up is to enliven proceedings and encourage those present to action.
What's the origin of the phrase 'Gee-up'?
The first of the two meanings given above derive straightforwardly from the word 'gee', which was the command used to direct the movements of horses and oxen. The childish name for a horse - 'gee-gee' of course derives from the gee command.
'Gee' and 'ree' were used to guide the animals to the left and right. These commands were used since the early 17th century in the UK, as in this example from 1628 John Earle's Micro-cosmographie, 1628:
He expostulates with his Oxen very understandingly, and speakes Gee and Ree better then English.
'Gee-up' began as 'gee-hup', simply 'gee' with the intensifier 'hup'. Its first appearance in print that I can find is from the English newspaper The Chester Chronicle, October 1776, in the prologue of a play entitled New Brooms:
Your late old coachman, tho' oft splashed by dirt,
And out in many a storm, retires unhurt,
The road is not all turnpike - and what's worse is,
They can't insure your watches or your purses,
But they'll insure you that their best endeavour
Shall not be wanting to obtain your favour,
Which gained - Gee up! The old stage will run for ever!
It might be assumed that 'gee-up' is the source of the American 'giddy-up'. There's no clear connection between the expressions though; the latter being a 20th century invention with no known link to the earlier British gee-up.
The 'gee things up' form of the expressions is more difficult to explain. It may be that this is just a variant of 'gee-up' - both expressions relate to 'getting things going'. It is also possible that 'gee things up' is a variant of 'ginger up' - again both expressions have much the same meaning. However, I can find no evidence that links 'geeing up' and 'gingering up' and the similarity of the two could be coincidental.
See other phrases that were coined in the USA.