self-deluded (adj.)

word forming element indicating "oneself," also "automatic," from Old English use of self (pron.) in compounds, such as selfbana "suicide," selflice "self-love, pride, vanity, egotism," selfwill "free will." Middle English had self-witte "one's own knowledge and intelligence" (early 15c.).

OED counts 13 such compounds in Old English. Middle English Compendium lists four, counting the self-will group as a whole. It re-emerges as a living word-forming element mid-16c., "probably to a great extent by imitation or reminiscence of Greek compounds in (auto-)," and formed a great many words in the pamphlet disputes of the 17c.

"deceive, impose upon, mislead the mind or judgment of," c. 1400, from Latin deludere "to play false; to mock, deceive," from de- "down, to one's detriment" (see de-) + ludere "to play" (see ludicrous). Related: Deluded; deluding.

Mislead means to lead wrong, whether with or without design. Delude always, at least figuratively, implies intention to deceive, and that means are used for that purpose. We may be misled through ignorance and in good faith, but we are deluded by false representations. A person may delude himself. [Century Dictionary]