addendum

the word 'addendum' is a direct borrowing from latin, where it is the neuter gerundive form of the verb 'addere', meaning 'to add'. the gerundive suffix '-endum' gives it the sense of 'a thing that is to be added'. this grammatical construction was used in latin to form nouns from verbs, specifying an object of necessity or obligation. entering english in the late 17th century, primarily in scholarly and legal contexts, it retained its precise meaning of an item that is appended to a main work, such as a book or contract, to provide supplementary information.

Structure: add (to add) + endum (thing to be) - add: from latin 'addere', meaning 'to add, to give to'. - endum: a latin gerundive suffix, indicating something that is to be done or must be done, forming a neuter singular noun.