compurgator

Compurgator is a descendant of the Latin verb compurgare, meaning "to purify wholly." The root of that word, "purgare," also gave English "purge" ("to clear of guilt," "to cause evacuation from," or "to get rid of") and "expurgate" ("to cleanse of something morally harmful, offensive, or erroneous"). "Compurgator" has occasionally been used in a more general sense of "one who supports or defends another," but its primary application is to the specific legal situation in which someone appears in court as a character witness for the defendant. "Compurgator" has been used in English with this specific legal meaning since the 16th century.