Genuine etymological mysteries. Nobody, including professional lexicographers, actually knows for certain where these came from.
36 idioms in this category
"Behave properly; be on your best manners."
Still a Mystery"Raining extremely heavily."
Still a Mystery"To reveal a secret, often accidentally."
Likely Origin (Disputed)"An extremely small or cramped space."
Likely Origin (Disputed)"A shameful secret kept hidden, usually within a family."
Likely Origin (Disputed)"An elaborate, implausible tale."
Still a Mystery"An exclamation of surprise, frustration, or exasperation."
Still a Mystery"Extremely pleased or delighted."
Still a Mystery"To talk incessantly or excessively."
Still a Mystery"A miscellaneous collection of small items."
Still a Mystery"A question asked to someone who has suddenly gone quiet or is unable to speak."
Still a Mystery"Dressed extremely smartly or elaborately, making a real effort."
Still a Mystery"Something or someone considered excellent, the best."
Still a Mystery"To succeed, or to meet the required standard."
Still a Mystery"To be knowledgeable and experienced about a subject."
Still a Mystery"Annoyed, fed up, or irritated."
Still a Mystery"A complete mess or muddle."
Still a Mystery"Extremely and openly pleased, especially about a success."
Still a Mystery"An obvious problem or difficult topic that everyone is avoiding discussing."
Still a Mystery"Extremely happy; euphoric."
Still a Mystery"To tease someone, especially by telling them something untrue as a joke."
Still a Mystery"Everything; the entire thing, with all its parts included."
Still a Mystery"To watch something or someone closely."
Still a Mystery"In perfect health or good order."
Likely Origin (Disputed)"To avoid committing to either side of a decision or argument."
Likely Origin (Disputed)"Very rarely."
Still a Mystery"Used to say something will never happen."
Still a Mystery"To shatter someone's illusions, hopes, or fantasies."
Still a Mystery"Something very easy to do."
Still a Mystery"To solve one financial problem by creating another, usually by taking from one source to cover a different debt."
Still a Mystery"To attract all the attention, outshining everyone else in a performance or event."
Still a Mystery"To do something completely and thoroughly, holding nothing back."
Still a Mystery"To lose your nerve and back out of a plan or commitment at the last moment."
Still a Mystery"A carefree, comfortable existence, free from worry or hardship."
Still a Mystery"To deceive or trick someone."
Still a Mystery"Eccentric, erratic, or wildly unpredictable."