FLORENCE.  m. Anglicized form of Irish Finghin (q.v.), meaning "fair offspring." 

FLORENCE.  Unisex.  Anglo-Norman, from Latin Florentius, meaning "flourishing."  It appears in Arthurian legend as the name of a son of Gawain. (The Story of the Grail and the Passing of Arthur, Pyle, 1913).
    m.  Nicolas-Joseph Billot de La Ferrière, stage name Florence (d. 1816), was a French actor.  Florence (d. 1118), a monk of Worcester.
    f.  Florence Nightingale (d. 1910), was an English nurse, statistician and writer.  Florence Henderson, an American actress and singer. (Wiki)

... As an Angevin saint, Florentius accounts for the prevalence of Florence in the masculine gender among the Anglo-Norman nobles of the middle ages; but it soon died away.  The later revival is chiefly owing to the name having been given to English girls born at the Italian city so called, and it acquired a deeper and dearer honour in the person of Florence Nightingale...
    ... Finghin M'Carthy Anglicized himself as Florence, in which he was afterward imitated by his countrymen, though the change did not bring him much good fortune, as his enemies represented that his alias showed sinister intentions; and for other more definite misdeeds, he was thirty-six years imprisoned in the Tower of London.  It was a mistake in Lady Morgan to make Florence M'Carthy a woman, for Florence and Flory in Ireland were always men.  We do find a Florence mentioned as contemporary with St. Patrick; but this is doubtless meant as a translation of Finghin... (History of Christian Names, Yonge, 1884)