Apparently the duo was considered part of the family.
We need mention only the chief of them - the Collectio Anselmo dedicata, by an unknown author of the end of the 9th century; the Libri duo de synodalibus causis et disciplinis ecclesiasticis, 3 compiled about 906 by Regino, abbot of Pram, and dedicated to Hatto of Mainz, relatively a very original treatise; the enormous compilation surchard.
Have the usual meaning (Duo = u l - uo, L 2 uo = Du 1 - Auo, .
In the preface to his Arithmeticae libri duo et totidem Algebrae (1560) he says: " The name Algebra is Syriac, signifying the art or doctrine of an excellent man.
Dualis, containing two, from duo), a philosophical term applied to all theories which attempt to explain facts by reference to two coexistent principles.