Barmy (adjective)

1. Crazy or mad.
2. Extremely foolish or irrational.

Origin:

The word "barmy" comes from the old english word "beorma" meaning "yeast" or "froth", it was used to describe something frothy, crazy or wild. it was first used in the 16th century.

Examples:

1. The idea of jumping out of a plane seemed barmy to him.
2. He thought the plan was completely barmy and refused to go along with it.
3. The teacher thought the student's excuse for not doing his homework was barmy.
4. Some people thought his investment strategy was barmy, but it turned out to be very successful.
5. She thought the whole concept of a cheese-rolling competition was barmy.