Just as Joyce modeled Mulligan on his friend Gogarty, he modeled "Haines" on Gogarty’s other guest in the tower, a well-born young Englishman named Richard Samuel Chenevix Trench (1881-1909). Gogarty met Trench during a term at Oxford in early 1904, a fact which accounts for Mulligan's referring to "the oxy chap downstairs." Haine is French for “hate.”
Haines’ Englishness provides one possible basis for hearing his name as an indictment, but late in Telemachus Stephen sees that as Haines looks at him his gaze is "not all unkind," and in Nestor he thinks again that Haines' eyes were "unhating." So if we are to hear Haines' name as an indication that he is a hater, it appears to have more to do with the revelation, a few moments after Stephen's realization that Haines does not hate him, that the Englishman is anti-Semitic. In Scylla and Charybdis, Joyce will show that Mulligan too is anti-Semitic, though perhaps in a less virulent way than Haines.
In Circe, Mulligan celebrates a Black Mass assisted by "The Reverend Mr Hugh C Haines Love M. A." Haines here has become conflated with the Reverend Hugh C. Love, an entirely different (but similarly Protestant, upper-crusty, well-meaning, and insensitive) personage in the novel. The juxtaposition of their two names produces the meaning Hate Love.
Trench was an enthusiast for Irish language and native Irish culture. He was known in England as Samuel, but asked to be called Dermot (Diarmuid) in Ireland, and in 1905 he legally added that Irish name to his string of names. The friendship of Gogarty and Trench represented a kind of cross-Irish Sea chiasmus. Though settled in England, Trench’s family was Anglo-Irish, and Gogarty’s Catholic family moved in Dublin’s Anglo-Irish elite. After Gogarty attended Oxford for a term and returned to complete his degree at Trinity College Dublin, Trench reciprocated by visiting Ireland in September 1904. Into this insular harmony, Joyce interjected the continental dissonance of naming him Haines.
Trench’s third cousin once removed, an Irishman named C. E. F. (Chalmers) Trench, wrote an article titled “Dermot Chenevix Trench and Haines of Ulysses,” published in JJQ 13 (1975): 39-48. The essay makes clear how deeply passionate was Trench’s commitment to the cause of resuscitating the Irish language.