Why is it that the word “bread” is so often used as a slang term to mean either general sustenance or as a synonym for money? It makes sense of course that bread equates with sustenance or nutrition, we know that! It’s thought that the use of the word “Bread” as a synonym for money dates back to the 1930’s America. However, “earning a crust” and equating “dough” with money may go back as far as 1850’s England, according to the Oxford English Dictionary: "He thinks he will pick his way out of the Society’s embarrassments, provided he can get sufficient dough.”
People use slang words all the time, so it’s not that unexpected. In cockney rhyming slang “bread and honey” is shortened to bread, meaning money. The person who earns a wage to support their family is often referred to as the “breadwinner.”
“Dough” came on to the American slang scene in about 1840, and predated “bread” by a little more than a century. Other stories tell us that soldiers during the American Civil War demanded that part of their pay was a loaf of bread, which lends itself to the theory of how the term “dough” or “bread” came into use when referring to salary or money.
We see written evidence of “bread” as money in the 1930s, when it was used by some cultures; it remains an enduring American slang term.
Either way, bread is an important food that is part of a staple diet and an important source of nutrients. Where bread was the traditional everyday necessity of life in the 19th Century, to earn one’s living was to earn one’s bread, therefore bread became synonymous with money. When people had little else, they always had bread. Also, “earning a crust” was a way of describing basic pay – you mightn’t get a whole slice but at least you’d get the crust!
 The quote allegedly appeared in the Yale Tomahawk, a publication of Yale's Alpha Sigma Phi fraternity.