Smokey Stover, the 1935 "Where there's foo, there's fire" guy, was a TV cartoon in the 1970s. https://en.wikipedia.org/wiki/Smokey_Stover#Animation Influenced by german furchtbar/foobar/fubar, MIT used fu() and bar() in the late '30s.

The paper goes deeper

♫♫ "WHAT THIS COUNTRY NEEDS IS FOO" https://www.youtube.com/watch?v=W2pljKyCgwc

Paywalled link? Come on, we're past that. Here's the article:

https://sci-hub.st/10.1007/s13347-019-00387-2

Foo, Bar, Baz…: The Metasyntactic Variable and the Programming Language Hierarchy / by Brian Lennon