Dingus Billy Magee was written as a nineteen-year-old, and had to be re-written to accommodate Frank Sinatra's casting.
After completing this film, Frank Sinatra took a seven-year acting hiatus that ended with the TV movie Contract on Cherry Street (1977).
Dingus translates as a generic or unnamed "thing" or, in colloquial Yiddish, to use polite terms, as "penis".