It was first used as an interjection in the 19th century: “They marched, and I amongst them, to face the enemy – heads up – step firm – thus it was – quick time – march!”
Then, at the beginning of the 20th century, it began to be used adjectivally, as in: “He was always right on the job, and looking ‘heads up’.”
Then, around the late 70s, it became a noun, probably through shortening of phrases like “heads-up alert” into “heads-up”: “It is regarded as being a heads-up on a sale.”
"How it turns out" is also often phrased in the form of, "tell me how it went". "turn" and "went" are directly related, as "went" comes from an old word "wend", which means "turn".
Isn't that interesting? When you ask how something went, you are literally asking how something "turned" out.
Went is the past tense of go. Turn represents just that, rotation or revolution, a thing going.
Best Answer
Etymonline to the rescue: