"Irishtown" is a suburb that fronts Dublin Bay, south of the River Liffey and north of Sandymount. Its name dates to the 15th century, when the English rulers of Dublin became fearful of being outnumbered by natives and enacted statutes that banned Irish people from living within the city limits or doing business in the city past daylight hours. They built their own shabbier town outside the walls. "Strasburg terrace," where Stephen's "aunt Sara" (or "Sally") lives with her husband Richie Goulding and their children, is a distinctly un-posh patch of turf in Irishtown.
Today land has been reclaimed from the sea and Irishtown has expanded to the east, but in 1904 Strasburg Terrace was very close to the shore, so it would be easy for Stephen to turn northwest from Sandymount Strand and walk across the sands to his aunt's house. He stops and thinks about it: "His pace slackened. Here. Am I going to aunt Sara's or not?" After thinking about the scene that would greet him in the house, he sees his feet heading northeast toward the Pigeon House and realizes that he will not be visiting his relatives today. (Or staying the night. Since he thinks that he will not be returning to Mulligan's tower at the end of the day, it seems possible that he has been thinking of asking the Gouldings whether he could move in with them.)
Irishtown is featured again in Hades, when the funeral procession passes through it on its way from Sandymount to Glasnevin, and the men in Bloom's carriage spot Stephen walking through its streets past the "tenement houses." Bloom thinks back on the sighting in Aeolus: "Has a good pair of boots on him today. Last time I saw him he had his heels on view. Been walking in muck somewhere. Careless chap. What was he doing in Irishtown?" In Wandering Rocks the two old women that Stephen has seen on the beach walk back to Dublin "through Irishtown along London bridge road." Bloom also thinks about the area in Eumaeus.