Linebackers "hound" or "dog" the passer in a
football red dog, crashing through the line to try to break up a play.
When the tactic was invented in the 1960s, "red dog" was the signal given
in the huddle if one linebacker was to try cracking the line, "blue dog"
if two were to be used, and "green dog" if all three linebackers were to
charge. Football fans, however, misused the terms and applied red dog to
any rush through the offensive line, made by linebackers or linemen, and
that is what the term means today. It has also been used outside of
football for a rush on one person by a group of youths, usually drunk or
demented.