Old English sopp- "bread soaked in some liquid," (in soppcuppe "cup into which sops are put"), from Proto-Germanic *supp-, related to Old English verb suppan (see sup (v.2)), probably reinforced by Old French soupe (see soup (n.)). Meaning "something given to appease" is from 1660s, a reference to the sops given by the Sibyl to Cerberus in the "Aeneid."
Old English soppian, from the source of sop (n.). Related: Sopped; sopping.
The way things are properly and usually done: The SOP here is that you ask the chairman first
[WWII armed forces; fr standard operating procedure]
a morsel of bread (John 13:26; comp. Ruth 2:14). Our Lord took a piece of unleavened bread, and dipping it into the broth of bitter herbs at the Paschal meal, gave it to Judas. (Comp. Ruth 2:14.)