[muststopmyths]

"horn please", to tell people to honk while passing.

OK was originally a separate thing that used to occur in locations other than between the two words. I distinctly recall this from my childhood. Don't know the origins of it but there is some suggestion on the internet that it was copied from Tata trucks which had the logo of the OK soap (a lotus).

They could occur in the current order, but it was not necessary. It should still be read as separate from the "horn please" phrase.

As the country became functionally more illiterate over the years (yes, probably a controversial opinion :) ), the three words were just rote copied inline and painted on trucks, with the meaning lost to time.

[__rito__]

OK means: "On Kerosene".

See: https://trucksfloor.com/en/blog/horn-ok-please-on-indian-tru...

[muststopmyths]

I would love to see a reliable source for this. All I have ever found is people on the internet asserting this to be true, but no actual evidence (in the form of contemporaneous pictures or documents from WW2).