What is "heterophemy"

Heterophemy \Het`er*oph"e*my\, n. [Hetero- + Gr. ? voice, speech, fr. ? to speak.] The unconscious saying, in speech or in writing, of that which one does not intend to say; -- frequently the very reverse of the thought which is present to consciousness.
--R. G. White.

"the (unintentional) use of some other word or phrase in place of the one that was meant," 1875, from hetero- + Greek pheme "utterance" (see fame (n.)).

n. The use of one word or phrase when another is meant