Jack-in-office is a term primarily used in British English.
A jack-in-office is a self-important, rude, and/or petty minor official (or other person holding some authority). The plural is jacks-in-office.
You may recognise the word from the well-known painting by Edwin Landseer called A Jack in Office, and a character in Arthur Conan Doyle’s short story The Adventure of the Speckled Band calls Sherlock Holmes ‘the Scotland Yard Jack-in-office’.
Hannah McCall 
Interesting. I’ve never heard this term before. I like learning new terms. Thank you. 🙂
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No problem 🙂 it isn’t a term I was familiar with either.
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That’s really interesting. I love learning new British terms.
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I’m glad that I can provide some new British terms!
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These are really interesting, especially to an American like myself. Do you think this one has any relation to jackanapes, which is, I believe, a disrespectful or cocky person?
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I was thinking about this today. We also have jack-of-all-trades (someone who can do many types of work but isn’t necessarily good at any of them) and jack-the-lad (a brash young man who is a bit of a show off).
I have conducted a very small amount of research and they all seem to have different origins (or suggested origins). The explanation I am leaning towards is that they came into usage at a time when ‘Jack’ was often used as a generic name. Jackanapes was apparently originally Jack Napes and might have been the name for a tame monkey. Jack-the-lad might be based on the nickname of an 18th-century thief called Jack Sheppard (he escaped from prison a lot).
I feel that I could write an essay on this if I had time to investigate it properly …
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