Source: p 126, If I Was You..., Lauren Sussman, 2014
The third type of complement used with a transitive verb is an indirect object. It comes before a direct object and answers the question to whom? or for whom? after the subject and verb.
I ask not about the meaning of an indirect object, about which I've read, but about the rationale behind the nomenclature. Wikipedia's explanation is too feeble (as it concedes itself); how's he (as represented by him) only indirectly affected
? He received the present, so the sending affects him!
Indirect object | Entity
indirectly affected
by the action | She sent him a present.