Romain[e] may have started life as an Irish surname, but it became a French-speaking name somtime in the 20th century. Engish-speaking males married French-speaking mothers who transmitted the "mother tongue" to their male children who then married a francophone woman. This created a Romain[e]surname that continued to be French-speaking in future. The Sullivan surname went thrugh the same process. Since ROMAIN[E] and SULLIVAN were Irish and largely Catholic, they blended in quickly with the French Catholic "Acadien" or "Cajun" families that had been living in Nova Scotia since the early 1600's.
I think you know that METEGHAN should be pronounced as "meh-TAY-ghen". I believe it is the white man's rendition of a native Mi'kmaq (MEEG-maw) word.
I notice in another posting that you wondered about the surname GARRON. This surname is most common to the western and southern portion of Shelburne County, Nova Scotia, although it has now spread next door to Yarmouth County, and to the "big city" of Halifax, the capital city of Nova Scotia. Garron likely came to Nova Scotia from New England in the 1760's.