chalk

Almost certainly an extension of a chalk as a counting mark, which dates at least 400 years.

I’m fairly certain “chalk” among U.S. airborne soldiers refers to the practice of writing a plane number in chalk both on the plane fuselage and the helmets of soldiers who were assigned to that plane. 

It helped remove confusion about who belonged where during the scramble to board planes prior to an operation.

isn’t that a form of counting?

Well, more like a form of matching. 

I mean, if you say “We put three chalks out before the winds picked up and we had to scrub the rest,” then you’re counting because you’re relating a number of people who managed to jump.

If you walk up to someone and say “You’re in chalk three,” then you’re matching that person with a group and that group with a plane (or, I suppose, a helicopter).  Someone somewhere in the chain of command is using the number of chalks to count, but for everyone doing the jumping, the number is a designation.

And they don’t, at least in peacetime operations, still use chalk that way.  At least, they didn’t when I went through the basic airborne course at Ft. Benning in 1994, nor at Ft. Bragg, where I served as paratrooper on jump status.  They just tell you your chalk, point out your chalk leader, and you stick with that person.  That might vary by unit.  Most of my jumps were with signal units, but I had one with some artillery, one with some infantry, and one with some Special Forces people, none of which did anything more than have the jumpmasters say “From you to you—chalk one --- form up over there,” etc. 

I edited a book on airborne soldiers last year, and I turned to that just so you could fill out your references, but a scan of the final draft revealed that the sidebar we had about “sticks” and “chalks” was removed at the end for space considerations.

Good rule.  :-)

I never heard “chalk” being used for anything to do with wheeled transport, except in usages you might expect like “chalk leaders, load your chalks up on the cattle trucks, we’re running late.”

Other than that, referring to a chalk as a group assigned to a wheeled vehicle sounds like the kind of thing a bored drill sergeant might come up with to feel better about loading his trainees on the bus. 

I had one who controlled the chow hall line by saying “five jumpers to the left door,” in imitation of a jumpmaster’s instructions, instead of “five more can go in now.”