William H.A. Williams writes in 'Twas Only an Irishman's Dream: The Image of Ireland and the Irish in American Popular Song Lyrics, 1800-1920 (University if Illinois Press, 1996, pp. 41-42):

"Come Back to Erin" is another perennial favorite Irish song of parting, also written by a Briton -- Charlotte Alington Barnard (1830-69), who published her works under the pseudonym "Claribel." The song came out in 1866 and is an interesting example of how a skilled songwriter of the period could work into one piece so many of the elements that had come to define or signify the Irish genre for the popular market. They are all contained in the opening verse of the song, which then serves as the chorus.

Come back to Erin, Mavourneen, Mavourneen,
Come back Aroon to the land of thy birth,
Come with the shamrocks and springtime, Mavourneen,
And its Killarney shall ring with our mirth.

In the first line, Barnard uses the poetic expression "Erin," along with an already familiar Gaelic term of endearment. Another Gaelicism, "aroon," appears in the second line, along with the emphasis on "land of thy birth." The shamrock, not yet all that common in Irish songs, is referenced in the third line, as well as "springtime," thus associating Ireland and Irishness with the beauties of nature. This is reinforced in the last line by the reference to Killarney, already a well-known tourist attraction. In spite of the fact that the heroine is going to England rather than to America, the song was a great favorite in the Unted States, as were other of Barnard's songs, such as "I Cannot Sing the Old Songs."