Ontalethophobia is the fear that what is true is a reality; the fear of truth being a reality, not just something you think you know. Ontalethophobia is denial.
But what does Ontalethophobia mean literally? Ont is a greek root meaning in existence, and i roughly translated it into reality, and aleth, being a greek root for truth, coming from the word ἀληθής. Ontalethaphobia is not the same thing as alethaphobia, which is the fear of the truth itself, this is the fear that what you already know is true, is true, very similar, with key differences;