Not every idiom comes from a single grand event. Plenty are just old slang that stuck around, rooted in ordinary spoken English rather than a documented incident.
18 idioms in this category
"The whole thing; everything, with nothing left out."
Likely Origin (Disputed)"There you go; it's as simple as that."
Still a Mystery"Engaged in petty cheating, fraud, or dishonest dealing, especially for small personal gain."
Likely Origin (Disputed)"To mock, tease, or make fun of someone, often gently."
Still a Mystery"Ordinary, basic, without any special features."
Well Documented"To put in more effort or power, especially when driving or exerting physical force."
Well Documented"Not very intelligent, or not quite right in the head."
Well Documented"To have a chat, especially a long or gossipy one."
Still a Mystery"To be extremely frightened or nervous."
Still a Mystery"To be very expensive."
Well Documented"To pursue a mistaken assumption or the wrong course of action entirely."
Well Documented"To get straight to the point, skipping unnecessary detail."
Well Documented"To carry a grudge or a persistent, defensive resentment, as if spoiling for a fight."
Likely Origin (Disputed)"Extremely pleased or delighted."
Likely Origin (Disputed)"The genuine, authentic thing, not an imitation."
Well Documented"A near success that still falls short of actually winning or succeeding."
Well Documented"To take on more responsibility or work than you can actually handle."
Likely Origin (Disputed)"To leave, or set off on a journey."