placitum (plas’i-tum), n.; pl. placita (-ta). [ML. see placit, plea.] In the Middle Ages, a public assembly of all degrees of men, where the sovereign presided, usually summoned to consult upon great affairs of state; hence, a resolution taken by such an assembly; also, a penalty or fine, or a plea or suit.

Source: The Century Dictionary Online.

Nor, for that matter, could I call Salvatore’s speech a language, because in every human language there are rules and every term signifies ad placitum a thing, according to a law that does not change

Source: The Name of the Rose by Umberto Eco.