The 7th child of Wm. FARNSWORTH and Martha HENDERSON, is listed as a 1-year-old male in the 1860 Newton County, AR census. He is blind. His name is N. W.
I suspect his name was Nathaniel W. FARNSWORTH. Nathaniel was a popular given name in the HENDERSON family.

N.W. does not have any meaning pertaining to any disability.

Where were these FARNSWORTH children in 1870 census? I believe their father remarried in 1867 to a Irene/Irena (CHANDLER) TUTTLE and was in Wiscosin with his second wife and their children and her children -- at least according to some trees I've seen.