?There is nothing to suggest when it was written.
Published 1866 (1 May), Fortnightly Review
The text is reprinted in Julian Thompson's Anthony Trollope: The Complete Short Stories (Carroll and Graf, 1992), with the following headnote
Originally appeared in The Fortnightly Review, 1 May 1886. This burlesque was not reprinted in Trollope's lifetime, and is his ony contribution to the mid- Victorian cult of sham medievalism. It might be compared with the squib "Crinoline and Macassar" in The Three Clerks (1858), which Charley Tudor is supposed to have written for The Daily Delight.
Trollope's "Gentle Euphemia" compares well with Jane Austen's Juvenilia: there is the same knockabout farce quality, the same crudity, the same exposÚs of the typical drunkenness and hardness of people's real language to one another, the same send-up of the normal level of sentimentalism disguised as the way courteous people really talk in bourgeois fiction. Trollope enjoys himself with epigraphs too. He thinks them ostentatious and shows a real facility for punning: that is, in several of the cases he invites the reader to read what was originally an innocent line as a salacious one, mocks assertions of morality and obedience (on the part of wives), and sees the "high style" as unendurably pompous (Milton -- though, as in the case of Jane Austen who mocks something in her Juvenilia, which she shows respect for and a love of elsewhere, elsewhere Trollope's reading and quotations from Milton shows he respected and loved the man's poetry).