Taking books to the librarian's daughter?

[Homey]

English Language Tests, Intermediate level

ESL/EFL Test #280 "English Slang Idioms (2)", question 1

"Keep your shirt .......... We'll figure it out. There's no cause for alarm," Jimmy told his boss when the computers stopped working suddenly.

(a) out
(b) down
(c) on
(d) off

English Language Tests, Intermediate level

ESL/EFL Test #280 "English Slang Idioms (2)", answer 1

"Keep your shirt on. We'll figure it out. There's no cause for alarm," Jimmy told his boss when the computers stopped working suddenly.

Correct answer: (c) on
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what does the idiom,"taking books to the librarian's daughter is like carrying coals to Newcastle" mean and where did it originate

[Mister Micawber]

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The idiom is 'CARRY COALS TO NEWCASTLE.
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Native English teacher at Mister Micawber's