Where does the nautical term sheet come from?

Answer 1

a sheet or sceata in Anglo saxon was at first a sail or the lower part of a sail at least& indeed this sheet has the same source as a bed sheet

the rope that controls a sail was known in those days as a sheet line or sceatline

but by the early 14th century sheet lines began to lose their lines & became just sheets

later sails stopped being called sheets & began to be called sails likely to distinguish them from their sheets