According to the Encyclopedia of New York City, a farm that covered a large part of the district now called Chelsea, was "bought on 16 August, 1750 and named Chelsea by Thomas Clarke, a retired British army captain." He presumably named it after a place in England. I believe that there is a Chelsea district in London.
The farm was later inherited by Clement Clark Moore, author of A Night before Christmas.
George A. Thompson
Author of A Documentary History of "The African Theatre", Northwestern Univ. Pr., 1998.