Definition - A noun or a noun equivalent, such as a pronoun, that is governed by either
(1) an active transitive verb or
(2) by a preposition.

Example -
In the sentence Bob kicked him the ball, the word ball is a direct object and the word him is an indirect object.

Etymology -
The word derives from the Medieval Latin objectum, thing put before (the mind or sight) (from ob, against + jacere, to throw).

Oxford English Dictionary -
Its first citation is from 1727:
"Verb Neuter, is that which signifies an action that has no particular object whereon to fall; but which, of itself, takes up the whole idea of the action."
(Chambers Cycl. s.v. Verb)

Please comment