Gifford suggests that the old woman's “Are you from the west, sir?” refers to the Gaeltacht, those isolated regions in western Ireland where Irish remained the native language, spoken by residents either solely or in conjunction with English. Mulligan’s mocking question, “Is there Gaelic on you?,” is “A west-of-Ireland, peasant colloquialism for ‘Can you speak Irish?’”—
Gifford, Don and Seidman, Robert J. Ulysses Annotated: Notes for James Joyce's Ulysses. Berkeley: University of California Press, 2008. Print.