Definition - The habit of referring to yourself in the third person.
Note: Originally, it denoted the excessive use of the pronoun he when referring to yourself. Someone who does this is called an illeist.

Example -

Reporter to Ricky Henderson: "Are you an illeist?"
Ricky Henderson: "Yes, Ricky Henderson is an illeist."

Etymology -
The word derives from the Latin ille, that (one); thus illeism is "that one-ism."

Oxford English Dictionary -
Its first citation is from 1809–10:
"For one piece of egotism … there are fifty that steal out in the mask of tuisms and ille-isms."
(Coleridge Friend (1818) I. 36 )

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