from
Bouvier's Law Dictionary, Revised 6th Ed (1856)
CONTUBERNIUM, civ. law. As among the Romans, slaves had no civil state,
their marriages, although valid according to natural law, when contr acted
with the consent of their masters, and when there was no legal bar to them,
yet were without civil effects; they having none except what arose from
natural law; a marriage of this kind was called contubernium. It was so
called whether both or only one of the parties was a slave. Poth. Contr. de
Mariage, part 1, c. 2, Sec. 4. Vicat, ad verb.