I'll assume it's still worth giving the full letter even though we have a later article by him.

The second account is by Charles Nordhoff in 'The Merchant Vessel' (1855) of loading at mobile about 1848:
'Five hands compose a gang, four to work the screws, and one to do the headwork.....The foreman begins the song, and at the end of every two lines the screw is forced to make one revolution, thus gaining perhaps two inches. Singing, or 'chanting', as it is called, is an invariable accompaniment to working in cotton, and many of the screw- gangs have an endless collection of songs, rough and uncouth, both in words and melody, but answering well the purpose of making all pull together, and enlivening the heavy toil. the foreman is the 'chanty-man' who sings the song, the gang only joining in the chorus, which comes in at the end of every line, and at the end of which again comes the pull at the screw handles. One song generally suffices to bring home the screw, when a new set is got upon the bale, and a fresh song is commenced.
'The 'chants', as may be supposed, have more rhyme than reason in them. the tunes are generally plain and montonous, as are most of the capstan tunes of sailors....The men who yearly resort to Mobile Bay to screw cotton are, as may be imagined, a rough set. they are mostly English and Irish sailors, who, leaving their vessels here, remain until they have saved a hundred or two dollars, then ship for Liverpool, London, or whatever port may be their favourite, there to spree it all away, and return to work out another supply.'

Thus, in 1844, Hill recognised 'shantier' as a french word; in 1848 Nordhoff found the term as 'chanty-man'; neither used 'shanty' for the song itself, although Nordhoff commented on the similarity of the screw-gang songs to the capstan songs afloat. By 1861 the shanty-man's song had become the shanty. the word 'shantyman' and ;shanty' are ceretainly American in origin, and belong in the 'Dictionary of American English'.                         JOHN LYMAN