Wetback is a erogatory term for a person that has immigrated illegally to the United States. Commonly referring to Mexicans and people who may have crossed the border illegally, the term is based on the presumption that the person in question swam or waded across the Rio Grande to get into the United States, getting his or her back wet in the process. The English term was first used in 1920s and saw official use by the U.S. Government in 1954 with Operation Wetback.