1) A useful or necessary house, commonly a privy or toilet, abbreviated by dialect speakers who refer to it as the 'nessy'.
1717 order that a necessary house be built in some convenient place, York
1743 pulled down a necessary house next the town gate, Gargrave
1788 A Boy about 12 years old ... hang’d Himself in the necessary House, Slaithwaite. In July 1785, an Ovenden farmer was in the lathe Croft Cleaning the Necessaries, and in August 1815 he was paid 2s for Thatching Jos Blagbrough’s Necessary. The OED evidence dates from 1609 but the word has a much longer history: 1413-4 ‘for one iron bar purchased from Robert Smyth for the door of the privy’, Selby.