What is the X in X-mas?
1590s, "a wandering, straying," from Latin aberrationem (nominative aberratio) "a wandering," noun of action from past participle stem of aberrare "to wander out of the way, lose the way, go astray," from ab- "away" (see ab-) + errare "to wander" (see err). Meaning "deviation from the normal type" first attested 1846.
aberration ab·er·ra·tion (āb'ə-rā'shən)
A departure from the normal or typical.
A psychological disorder or abnormal alteration in one's mental state.
A defect of focus, such as blurring in an image.
An imperfect image caused by a physical defect in an optical element, as in a lens.
A deviation in the normal genetic structure or number of chromosomes in an organism.