late 14c., "to join or unite (something to something else)," from Latin addere "add to, join, attach, place upon," literal and figurative, from ad "to" (see ad-) + -dere, combining form meaning "to put, place," from dare "to give" (from PIE root *do- "to give").
The intransitive meaning "to do sums, do addition" also is from late 14c. Related: Added; adding. To add up is from 1754; in the figurative meaning "make sense," by 1942. Adding machine "machine to cast up large sums" is from 1822.
<a href="https://www.etymonline.com/word/Added">Etymology of Added by etymonline</a>
Harper, D. (n.d.). Etymology of Added. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/Added