What is Infortiatum?

Legal Definition
Civil law. The second part of the Digest or Pandects of Justinian, is called infortiatum: see Digest. This part, which commences with the third title of the twenty-fourth book, and ends with the thirty-eighth book, was thus called because it was the middle part, which, it was said, was supported and fortified by the two others. Some have supposed that this name was given to it, because it treats of successions, substitutions, and other important matters, and being, more used than the others, produced greater fees to the lawyers.
-- Bouviers Law Dictionary
Legal Definition
The name given by the glossators to the second of the three parts or volumes into which the Pandects were divided. The glossators at Bologna had at first only two parts, the first called "Digestum Vetus," (the old Digest,) and the last called "Digestum Novum," (the New Digest.) When they afterwards received the middle or second part, they separated from the Digestum Novum the beginning it had then, and added it to the second part, from which enlargement the latter received the name "In-fortiatum." Mackeld. Rom. Law, ยง 110.
-- Black's Law Dictionary