away with the fairies
humorous informal phrase

- out of touch with reality

Collins Dictionary

- If you describe someone as being away with the fairies, you mean that they are crazy, have foolish or unreasonable opinions, or do not notice things around them.

The Free Dictionary

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ORIGIN

Apparently of Irish-English origin, meaning to give the impression of being mad, distracted, or in a dreamworld.

This phrase ultimately refers to the belief that the fairies spirit away human beings

Away with the fairies was first evidenced in print in a trail account at Drogheda, County Louth, Ireland in 1907.

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SYNONYMS

away with the pixies, not all there, lost in thought, distracted, daydreaming, in a dream-world, johnny head-in-air, out there, out to lunch, in one’s own world, deep in thought, absent-minded, miles away, in the clouds, with one’s head in the clouds, on the moon, off the planet, wool-gathering

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SMUGGLE OWAD into a conversation, say something like:

“I’m sorry Jim, I was momentarily AWAY WITH THE FAIRIES, can you please repeat that?”