Origin of the phrase "under your belt"?

Solution 1:

The Online Etymological Dictionary says:

To get something under (one's) belt is to get it into one's stomach.

The Oxford English Dictionary says:

Colloq. phr. under one's belt, in one's stomach. Also fig.

Their first three citations are:

• 1839 The Spirit of the Times: Away we went, each bearing, under his belt, his full share of the antifogmatical?compound.
• 1938 A Dictionary of American English on historical principles: Belt, v.? To put under one's belt; to swallow.
• 1954 The Manchester Guardian Weekly: His wife had 135,000 miles driving in the States under her belt?but was still failed.

Here's three earlier literal examples, all about a lot of alcohol under one's belt.

• 1762's The Young Hypocrite by Samuel Foote:

• 1790's The Expedition of Humphry Clinker by Tobias Smollett (first published 1771):

• 1817's Ormond, a tale by Maria Edgeworth:

Solution 2:

The literal meaning of having something under your belt is having it in your stomach, but it’s probably more frequently used figuratively, to mean having acquired something, often intellectual. For example, the OED has these two supporting citations, from the English novelists P G Wodehouse (1954) and John Wain (1962):

Just as you have got Hamlet and Macbeth under your belt

He wanted me to get plenty of Latin and Greek under the belt so that I could be like him.

Below the belt has a quite different meaning. It’s from the language of boxing, where the rules forbid hitting the lower abdomen. It, too, can be used figuratively to describe other kinds of unfair act.