Slang term for a white man, originating, according to a comment
in the book "Beneath the underdog" by
Charles Mingus, (not verbatim)
"A white man
looking for a prostitute in early 20th Century Harlem who, because he didn't want to get out of his car to call a girl, he just honked to get the girls attention"
I think this is the most plausible definition.