add-on

The term 'add-on' is a modern English compound formed from the verb 'add' and the adverbial particle 'on'. The verb 'add' originates from the Latin addere, a combination of ad- ('to') and dare ('to give'), literally meaning 'to give to'. The particle 'on', with its Old English roots denoting position or direction, intensifies the sense of attachment or supplementation. In the mid-20th century, this phrasal verb was nominalized, particularly in commercial and technological contexts, to describe an optional extra component that is physically or functionally attached to a primary system. The logic perfectly captures the concept of something given (added) to sit upon or work in conjunction with (on) an existing base.

Structure: add (verb) + on (adverb) add: From Latin addere ('to put to, join, attach'), via Old French and Middle English. Functions as the core verb root. on: From Old English on, an ('in, into, onto, upon, toward, against'). Functions as an adverbial particle modifying the verb.