quaternio

But from the being of God and the being of creatures, a universal idea of being can be abstracted and predicated univocally of both the finite and the infinite; otherwise we could not infer from the existence of finite things the existence of God, we should have no proof of God's existence, as every syllogism would contain a quaternio terminorum.

The Catholic Encyclopedia, Volume 5: Diocese-Fathers of Mercy 1840-1916 1913

Once prepared, the parchment (membrana) was cut into leaves which were folded in two; four leaves together formed a book of eight folios (quaternio); all the books formed a codex.

The Catholic Encyclopedia, Volume 9: Laprade-Mass Liturgy 1840-1916 1913