Learn English – Origin of the term ‘country mile’

Strictly speaking "souls on board" has a different meaning from all of your other constructions.

"There are 150 on board" can't be turned into a question. The official phraseology is "say souls on board [and fuel remaining]" -- there are no questions in ATC official phraseology. "Say number onboard" really is ambiguous and could be understood to mean only passengers.

Strictly speaking, "people" or "humans" is ambiguous too. For example is a dead person still a person? This is a rational concern with "say passengers onboard" (which might not include crew) and "say number onboard" (which is ambiguous).

But nobody with any functioning brain cells could possibly misunderstand "say persons onboard". This is an officially-acceptable civil aviation alternative to "souls onboard", as are the written abbreviations SOB and POB.

There is actually a dispute over whether "souls on board" should count entire human remains. The civil aviation standard is that a dead body is cargo and not counted. The RAF standard, and that of many other military organizations, is that dead bodies are "souls" being returned and they count them. Whether that makes sense depends on exactly what the figure is for. Is it to know how many bodies to look for? Is it to know how many people perished? (Perhaps it does not matter so long as both sides know what they're doing, and they make this a point of respect.)

In any event, no more detailed origin is known, as far as I've been able to tell. There's just lots of speculation. It was definitely originally a nautical term.

Tom Dalzell’s The Routledge Dictionary of Modern American Slang and Unconventional English says the word dukes for fists in “put up your dukes” was attested as early as 1859. Dalzell says that forks was slang for fingers, and suggests that forks became dukes by way of the rhyming slang “Duke of Yorks”.

Credence is lent to this theory by Albert Barrère and Charles Godfrey Leland’s 1890 edition of A Dictionary of Slang, Jargon & Cant, which attests the very similar slang expression “put up your forks” meaning to challenge to a fight. (To put one’s forks down, however, was to pick a pocket!)

More corroboration comes from the 1859 The Vulgar Tongue: a Glossary of Slang, Cant, and Flash Words and Phrases by “Ducange Anglicus” (a wonderful pseudonym which loosely translates as “English dictionary”). “Anglicus” attests the verb fork in the phrase “fork out the tin” meaning “hand out the money”, used in London between 1839 and 1859. (Fork out is surely cognate with today’s idiom fork over.) This puts fork at the right place and time to make it possible for Cockney rhyming slang to invoke the noble Duke of York exactly as suggested by Dalzell.

However, the intermediate phrase “put up your Duke of Yorks” is theoretical: not attested in any text of which I am aware, which still leaves open the possibility of some alternative origin for the term.