A heads-up is one of those slangy terms that are disreputable not from their semantic content but from the company they keep. It is a cliché in the mouths of dull management types. The meaning has changed in its short life. Currently it means ‘an informal briefing’: ‘I’ll just give you a heads-up on the development of the budget compliance procedure.’ It used to mean ‘an advance warning’.
As with most clichés, the origin of the dead metaphor is unknown to its users. It seems to be from aeronautics. A head-up visual display was one by which a pilot could read his instruments without averting his eyes from the course of the aircraft. The term has been in use since at least 1960. By the 1970s, motorcar manufacturers were using it. Examples may be found under the 73rd meaning of the word head in the OED. Head is a busy word.
The plural form, heads-up, soon came to dominate. Perhaps it was influenced by heads, the obverse side of a coin, which has been used more frequently in the plural for as long as it has been recorded, that is, from the late 17th century.
By the 1980s, heads-up was being used as a noun, meaning a warning, not necessarily of anything bad. It might be a nod on a future sale. From this developed the main current sense of ‘an informal interim report’.
Entirely separately the verb head up emerged, a variant of head in the sense of ‘lead’ or ‘command’. Head up came from America, in the 1940s probably. By the 1970s an advertiser in the Daily Telegraph felt able to announce: ‘We need women who can head up the book department of several of our branches.’
Head up is related to head as next up is to next. On television shows, presenters say: ‘Next up, Myleene Klass on keeping your figure after a pregnancy.’ Somehow up makes it sound cooler.
Since the derivation of the noun heads-up is unknown to most who use it, they can easily suppose it to be connected to the phrase chin up, an exhortation not to give way to depression that came into use before the second world war.
Up in itself has aspects of cheerfulness among its thickets of meaning: up and running, cheer up, uplifting, on the up, tee up. Or perhaps the negative connections spring to mind, as in snafu. That’s life, as Chaucer says: ‘Now up, now doun, as boket in a welle.’