Dime a dozen is an expression for things that are so common, that they are of very little value, essentially being sold for less than a cent a piece.
A dime is a term for ten cents, often encountered in the United States, similar to quarter.
In real life practice, “dime a dozen” products include eggs, apples or other common, inexpensive goods.
Alternatively, the phrase may be used to refer to something that is so incredibly mainstream and worthless, that it may be easily acquired for a “dime a dozen”.
The first time the dime was minted in the United States was in 1796 and during the 19th century, several aforementioned goods, such as eggs, vegetables and fruits were marketed as a “dime a dozen”, embedding the expression into the minds of Americans.
It was at this time, that the meaning of the phrase had shifted from “a good deal” to an “overly common product, that is very little in value”.
The first ever printed documentation of the phrase originates from the 1930’s, and at this time it is utilized to belittle the product; deeming it frequently encountered and unremarkable.
The expression had been first defined on Urban Dictionary in 2003.