To me, a “klick” is one kilometer and a “click” is the next detent either way on a rifle sight to move the point of impact 1 inch at 100 yards. In my experience, “clicks” were only used at a rifle range. Once we got our combat zero (200 yds for me), Tennessee windage took care of the rest.
Why do we say 1,000 kilometers? What’s wrong with 1 Megameter?
In any context where distances of a significant number of megameters are common, the term is in fact used. Such contexts just aren’t very common, on the surface of our planet (which is only 20 megameters between antipodal points).
When speaking over the radio mike is short for minutes. “Hold 10 mikes” is understood to mean standby for 10 minutes. You don’t have to establish that mikes means minutes and not McNuggets.
That said, I do recall Heinlein making a sideways reference to “bought the farm”, something about people dying having made land purchases or agricultural deals. I read it about 15 years ago, so I’m fuzzy nowadays.
I always assumed it was a whole lot older – that it referred to the Roman Empire paying accumulated salary & bonuses to a centurion upon retirement, often including a plot of agricultural land in the rural area of the Empire. Or paying this to the widow of a long-term soldier killed in battle.
Yeah, he did that a lot. The part that was new for me was when someone said “bought the farm, or a piece of one” to refer to someone dead or severely injured (enough to be done with battle).