Sarnie is a slang term for SANDWICH, originating in the United Kingdom. It is believed to have been derived from the word 'SANDWICH, ' which was first used in the 18th century to describe a snack made of two slices of bread with a filling between them. The term has since become popular in other English-speaking countries, such as Australia and New Zealand. In the United States, it is sometimes used to refer to a submarine SANDWICH.