The pieces of bread in a sandwich are referred to as slices or sheets of bread . The snack is thought to have been made first for the Earl of Sandwich , hence the name . The open-faced sandwich also has a history differing from that of the true sandwich , having originated between the 6th and 16th centuries , with stale slices of bread used as plates called `` Trenchers '' ( whereas its relative , the modern sandwich , traces its roots to the Earl of Sandwich instead ) .