This is the word, me•shu•ga, crazy. It may be used as name-calling to a person who acts in a surprising, unexpected, and seemingly illogical way, or seriously when describing a person who has truly lost his mind and is really crazy by common definition. Obviously, this is not the name psychiatrists and mental health professionals would use. The Bible, on the other hand, does!
Do you remember King David pretending to be crazy when he was in the hands of Achish king of Gath?
“And he changed his behavior before them, and feigned himself mad in their hands, and scratched on the doors of the gate, and let his spittle run down upon his beard. Then said Achish to his servants, ‘Behold, you see the man is mad; why then have you brought him to me? Have I need of mad men, that you have brought this fellow to play the mad man in my presence? Shall this fellow come into my house?'”
You are, for sure, familiar with the popular notion that being too wise or genius brings some to the brink of madness. This was said about the Apostle Paul in the Bible:
“As he thus made his defense, Festus said with a loud voice, ‘Paul, you are crazy! Your great learning is driving you insane!’ But he said, ‘I am not crazy, most excellent Festus, but boldly declare words of truth and reasonableness'”
Acting in an unexplained way may cause others to label it as ‘crazy.’ This may happen today, just as it happened in Jesus time when people spoke in tongues:
“If therefore the whole church be come together into one place, and all speak with tongues, and there come in those that are unlearned, or unbelievers, will they not say that you are mad?”