Hi. Actually this french expression comes from the Navy guys (from Italy precisely).

The true story:

This expression is about the fact that, in april 1940, in the Strait of Messina (Italy), a German u-boat believed that it was fired an English ship by its back. Instead, the u-boat torpedoed an Italian ship, the "Duce Benito" which was the flagship of his ally . . . This ship had all its bottom lined with steels. Then the torpedo (a Krupp one) broke up all the stern, and penetrated up to the kitchens. The legend says that it finished its run by sodomizing a cock which was unfortunatly tilted on the furnaces.
Fortunatly (for the cock), the torpedo didn't explose. But a leack invaded the reserve where 125.371 packages of noodles were stocked in order to feed 1.237 officers and 3 marines onboard, during all the cross of the Strait.
Actually, under the action of the sea water (already salted ah ah), the noodles began to swell and swell, all along the open breach . . . and then this spread sealed the leak!
Arriving at Reggio di Calabria, (front of Messina), people were able to see the saved Italian ship entering the port "lined with noodles".

I knew that story because my nephew is a french Marine.
But I wanna thank the author (with pseudo Elpepe) for this text; I translated in english the commentary he wrote in 2006 in this source: http://www.expressio.fr/expressions/avoir-le-cul-borde-de-nouilles.php

But you must know that In fact, the french word "nouille" is also a metaphore for penis (in slang language).
Not many French know that it is more a gay expression. ;)
Today, it means for someone that he got chance, that he is very lucky . . .

Sure!