mid-15c., originally "sediment deposited by seawater," probably from a Scandinavian source (compare Norwegian and Danish sylt "salt marsh"), or from Middle Low German or Middle Dutch silte, sulte "salt marsh, brine," from Proto-Germanic *sultjo- (source also of Old English sealt, Old High German sulza "saltwater," German Sulze "brine"), from PIE root *sal- "salt."