The term actant goes back to Tesnière (1959) and has been fairly common especially in European linguistics since the 1970s. However, the synonym argument is becoming more and more common.
In Tesnière's terminology, actants are opposed to circumstants, i.e. optional modifiers of the clause.
- Tesnière, Lucien. 1959. Éléments de syntaxe structurale. Paris: Klincksieck.
- German Aktant