I haven't read all of your website so there's a chance you're already aware of the following quote from the U.S Government Printing Office web page. I've also included the link to that page.
The area known as Swampoodle in Philadelphia which would be in the vicinity of 25th and Lehigh near the old Shibe Park was at one time an area of Irish immigrant concentration. However, given the source of the nickname in Washington D.C. (marshlands) I would guess that the name has no significant connection with "Gaeilge." Just old fashioned swamps and puddles. The same would characterize the Philadelphia area between the Schukill and Delaware in the 19th century.
"On the day that Abraham Lincoln was inaugurated President, March 4, 1861, the United States Government Printing Office opened its doors on H Street at North Capitol. The area was farmland gradually giving way to roads and buildings. Nearby Tiber Creek overflowed in wet weather, producing swamp and puddles, and gave rise to the neighborhood's nickname, 'Swampoodle.'" http://www.access.gpo.gov/su_docs/fdlp/history/macgilvray.html