There seems little doubt that Admiral Rodney is the man in question. The following is quoted from Andrew Kuntz's The Fiddler's Companion, which also gives much more background; a direct link is unfeasible as the search engine there returns no results for Rodney's Glory, so one must instead search for Rodney:

"The title "Rodney's Glory," explains O'Sullivan (1983), was derived from verses set to the tune by the poet Eoghain Rua Ó Súilleabháin in 1782, commemorating a naval battle fought that year in which George Rodney (d. 1792), then vice-admiral of Great Britain, encountered the French fleet under Admiral Comte De Grasse... Ó Súilleabháin served on The Formidable, a ship which saw some of the severest fighting and thus "Rodney's Glory" is a first-hand account."