heads up (chiefly American)
idiom, metaphor

- a warning that something is going to happen, usually so that you can prepare for it

- a short talk or statement about how a situation or plan is developing

Cambridge Dictionary

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WORD ORIGIN

Before it was used in phrases like "Can you give me a heads up" or "I'll give you heads up," this phrase was and still is used as a danger warning. This likely originated in the construction industry where the phrase is frequently used to warn workers of activities taking place above them, so as to avoid injury from falling building materials like bricks and pieces of wood.

The Random House Dictionary says "heads up" first appeared sometime between 1940 and 1950. However, there are references to it in periodicals as far back as 1914. It has several slightly different contexts:

- to be alert and wide-awake. In this context, it is sometimes used an adjective to describe a sports team that plays with a high level of concentration (They played heads-up football today.)

- a type of display screen (heads-up display) used in aircraft that shows images and information on the windscreen so that the pilot can keep his/her "head up" in order to read the data while flying.

- an advance warning (The company issued a heads up about its financial condition two days before publishing its annual report.)

This last is the most common usage meanwhile. It is used frequently in business, in both e-mail and telephone communications, to either tell someone that they will get advance warning or a piece of information beforehand (I'll give you a heads up when the report is ready to be printed) or to ask to be informed about something ahead of time (Can you give me a heads up before you send out that report?).

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SYNONYMS

let me know, give me advance warning

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