Throw Under The Bus - origin

Found this on another site - its no Dave Collins gamer, but give credit to William Safire.

The meaning of this distinctive American verbal phrase goes beyond “reject” or “dissociate from” to a more vividly figurative expression of “to damage a reputation; to use as a scapegoat.” For its origin, I turn to our leading popular slanguist, Paul Dickson, author of “Slang —the Topical Dictionary of Americanisms,” just deliciously updated. Origin?
He says he believes it to be back-formed from a baseball team’s clubhouse man, who called for the ballplayers to board the team bus with “Bus leaving. Be on it or under it.” The slanguicographer backs this up with a citation from a 1980 Washington Post article and offers another usage that extends beyond sports: the rocker Cyndi Lauper in 1984 was quoted as saying: “In the rock ’n’ roll business you are either on the bus or under it. Playing ‘Feelings’ with Eddie and the Condos in a buffet bar in Butte is under the bus.” (emphasis mine)

(DO) I've also heard TUTB is a play on the expression "throw yourself in front of a bus" to save someone else. As Lennie Briscoe might say about a skel, "That guy? I woulda thrown under the bus."