DE (off) + RANGE...to be off the mental range, be insane.
de range..sounds like de arrange...so disarrange and also when this happens you mentally get agitated
focus.on rang..sounds very similar to ragg..ragging is considered a insane activity now a days.
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derange = mad or half-minded. consider range in the word. range classify as good range and bad range. so the person who falls under both good range and bad range is half minded.
bring "g" from where it is in the word and put it upside down and convert it into "b" and place it before r, so it becomes "debraned" or "debrained" meaning loss of brain