This song comes from the controversial left-wing musical THE CRADLE WILL ROCK. Originally planned to be put on under the aegis of the Federal Theatre Project, a New Deal program, it eventually was shut down under the official reason of budget cuts in the program, but it was rumored that the virulent liberal streak running through the show & others under the Federal Theatre Project forced the closing. With their theater locked down & surrounded by armed guards, producer Orson Welles, director John Houseman & composer Marc Blitzstein rented another theater, and with practically no sets & only Blitzstein accompanying the cast, who sang from the audience since they were forbidden to perform the show onstage, the show went on. Even today, THE CRADLE WILL ROCK is performed with a bare-bones production similar to its premiere, and when it did receive a more professional mounting a few months later, it managed to run for 108 performances, a miracle given the show's content & the time it was performed. Songs like this, which poke at how easy it is set to laws & morals when one has food on their table & money in their pocket, have not dated since & are just as pointed today. Not surprisingly, that prevented most of the score from being recorded by others, although THE CRADLE WILL ROCK cast album was the first of a complete production to be recorded at the time (on a collection of 78s, since the LP had not been designed yet). One recording of interest, though, is P.J. Harvey's version of "Nickel Under The Foot", which was featured in the 1999 film CRADLE WILL ROCK, Tim Robbins' fictionalized account of the show's mounting.

Source: "A Standard A Day" by Eric Nichols Andrews

From "everythingmusicals.com"

When Blitzstein was working on The Cradle Will Rock, he played the song "Nickel Under the Foot" for friend and mentor Bertolt Brecht. The song is sung by Moll, the prostitute and symbolic heart of the show, and is a heartbreaking lament on the caustic effects of poverty:

And if you're sweet, then you'll grow rotten,
Your pretty heart covered over with soot.

The song also decries the actions of the supposedly upstanding people who surround Moll, and the ruthlessness with which they pursue personal gain:

Go stand on someone's neck while you're takin'
Cut into somebody's throat as you put.
For every dream and scheme's depending on whether
All through the storm, you've kept it warm.
The nickel under your foot.

Upon hearing the song, Brecht urged Blitzstein to use it as the central conceit of the show: prostitution, only not in the literal but rather the figurative sense. The stunning irony at the heart of The Cradle Will Rock is that the prostitute Moll is one of the only characters who doesn't sell out, who hasn't compromised her values, her talent, her dignity.