Dating of "mud flap"?

[Mullins, Bill]

On Mon, Jul 11, 2005 at 10:13:58PM -0400, Joel S. Berson wrote:
> When does "mud flap" date from?
>
> The Phoenix [Boston] July 8-14. 2005, 5/5
>
> BIG BURLESQUE'S FAT BOTTOM REVUE Talk about mud flaps, these girls have got
> 'em: San Francisco's "plush and plus-sized burlesque" troupe teams up with
> Northampton's Femmetastic Females, Boston's Black Cat Burlesque, BCB
> wrasslin' offshoot La Gata Negra, the Phat Fly Girls, and others for an
> evening of Rubens-esque ribaldry.

It sounds like the author is using the phrase as a euphemism for some part of a large black woman's anatomy.  

Are you asking about the first use of the euphemism, or the first use of the term to describe the devices that go behind the rear wheels of a vehicle?

LATEST CUSTOMS RULINGS.
New York Times; Mar 14, 1915; pg. XX12 col4.
"The Mead Cycle Company and others, Chicago, protested the Collector's classification on cycle lamps, pump clips, celluloid and metal bicycle pumps, push bells, tool bags, and mud flaps.  They were returned for duty under the Tariff act at 25 per cent, ad valorem, as "parts of bicycles." "