gob iron

gob iron (uncountable)

1. (slang) A simple harmonica
   • 2007, Here Comes the Sun, by Joshua M. Greene, P.9

     One kid drummed on a washboard, another plunked a broom-handle bass, a third faked chords on guitar, another blew into a gob iron (which was what they called a harmonica), and they dubbed themselves a band.

• bog iron