What's the origin of the phrase "fresh off the back"?

I often come across this phrase "fresh off the back of something" and although I could never find it in a dictionary, I figured out it means "right after something" but what does it really mean "off the back"? Why is the word "back" used in this phrase?

OED has a draft entry from 2010:

Chiefly Brit. on (also off) the back of : on the basis of; by capitalizing on the work or success of.

1906 Baily's Mag. Jan. 30/2 On the back of every successful form of enterprise kindred ventures are too often floated without much regard to the question of whether they contain the elements of success.
...
1993 Accountancy Oct. 49/1 Off the back of its tea business Moran diversified into freight.
2004 H. Kennedy Just Law (2005) xiii. 278 The government wins support for the entitlement card on the back of asylum scares.

I suppose it may come from horse-riding, referring either to riding on, or jumping off from, the back of an animal.

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