"Willy B" or "WillyB" or "WB" is Williamsburg, Brooklyn. It's also used for the Williamsburg Bridge. This is not to be confused with the "The WB" that is a broadcast network.
"Willy B" appears in a Google Groups message of January 31, 1995, about the Bridge. "WillyB" show up in December 8, 1996.
"Billburg" and "Billyburg" are both far more popular.
"Billyburg" shows up in a Google Groups post of November 7, 2001. "Billyburg" shows up in a Google Groups post of October 31, 1999.
Wikipedia: Williamsburg, Brooklyn
Williamsburg is a neighborhood of 113,000 inhabitants in the New York City borough of Brooklyn, bordering Greenpoint to the north, Bedford–Stuyvesant to the south, Bushwick and Ridgewood, Queens to the east and the East River to the west. Part of Brooklyn Community Board 1, the neighborhood is served in the south by the New York Police Department (NYPD)'s 90th Precinct and in the north by the 94th Precinct. In the City Council, the western and southern part of the neighborhood is represented by the 33rd District; and the eastern part of the neighborhood is represented by the 34th District.
Williamsburg is an influential hub of current indie rock, hipster culture, and the local art community. Many ethnic groups also have historically based enclaves within the neighborhood, including African Americans, Italians, Jews, Puerto Ricans, and Dominicans. The area is rapidly going through gentrification.