"Allen's Alley" was a popular bit in Fred Allen's radio shows in the 1940s. In Allen's Alley, Fred (often with his real-life wife, Portland Hoffa) would pose a question to four different people of various "humorous dialects", all living along the same alley. A typical bit would include chats with such luminous personalities as the pompous southern Senator Claghorn (the inspiration, in name and demeanor, for Foghorn Leghorn), the longwinded poet Falstaff Openshaw (voiced by Alan "Fred Flintstone" Reed), a New England farmer by the name of Titus Moody, or Mrs. Nussbaum, a busy Jewish mother.
Considering Allen was born and raised in Cambridge, and more than likely got his vaudeville start in Boston's theaters, I'm willing to bet that this alley was named in his honor, with his blessing, and I bet the location next to the Majestic (a famous vaudeville venue in its day) had something to do with it, too. And I bet that if it was named in his honor, there may have been a ceremony to go along with it. And I bet this ceremony was covered by the local papers... which means...
TO THE BOSTON PUBLIC LIBRARY I GO!
Don't tell Don Saklad!