"messenger, envoy," late 13c. (in Anglo-Latin); c. 1200 as a surname, from Anglo-French heraud, Old French heraut, hiraut (12c.), from Frankish *hariwald "commander of an army" or a similar Germanic source, from Proto-Germanic *harja "army" (from PIE root *koro- "war;" see harry) + *waldaz "to command, rule" (see wield). The form fits, but the sense evolution is difficult to explain, unless it is in reference to the chief officer of a tournament, who introduced knights and made decisions on rules (which was one of the early senses, often as heraud of armes, though not the earliest in English).
late 14c., "to sound the praises of," from herald (n.). Related: Heralded; heralding.