add (v.) Look up add at Dictionary.com
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 comb. form meaning "to put, place," from dare "to give," from PIE root *do- "to give" (see date (n.1)). 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," 1942. Adding machine is from 1874.