I just met this sentence "Your brother is constantly on your case for being clumsy, so when he knocks down a table filled with glassware, you revel in it".

I don't know why the phrase means "to be constantly nagging, harassing, or annoying someone".

  • Searching Google Books pre-1980 all instances of "on my case", "on his case" are about literal legal cases or other similar administrative matters. It starts to be used metaphorically in their sources in the 80s, primarily associated with teenagers, although there's an early use from a 1984 Hispanic Women's Health conference proceedings. If someone wanted to trace its path more accurately, there are sources available.
    – Stuart F
    Aug 14, 2022 at 13:36

2 Answers 2


Of the many meanings of "case", the OED has

7.c. An incident or set of circumstances under investigation by the police or a detective. cold case, murder case.

The use goes back to the 18th century:

1799 Oracle & Daily Advertiser 23 Feb. To render it incumbent upon the justice of that House to enquire into, and to investigate the case.

1954 E. S. Gardner (title) The Case of the Runaway Corpse.

If a detective were investigating a crime, he would be said to be "on the case" - taking an active interest in all people and things that might lead to a solution.

2022 "The Abandoned Room" Charles Wadsworth Camp· "I'm on the case because your grandfather died very strangely. He was murdered, very cleverly murdered."

The idea of "being on someone's case" thus = taking an active interest in something they are doing.

See also Urban Dictionary: I'm on your case

When someone is on another's case it means he can be stalking them or following them... just looking at what they are doing.

My Headmaster is always on my case

I'm on your case you asswipe.


Green’s Dictionary of Slang suggests that that the “case” in question is possibly the current state of your mind. The expression is of AmE Black origin:

get on someone’s case (v.) (also be on someone’s case, get down on someone’s case, stay on someone’s case) (orig. US black) to pester, to harass.

  • 1971 [US] H.E. Roberts Third Ear n.p.: case n. […] 2. .an imaginary region of the mind in which is centered one’s vulnerable points, eccentricities, and sensitivities; e.g. Don’t get on my case!

  • 1972 [US] E. Folb Urban Black Argot 137: Down on Someone’s Case to verbally harass someone.

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