Scottish word

[Roy Roebuck]

Why are Scotsman called Jock

[Quizmonster]

It is simply a Scottish variant of 'Jack', itself a by-word for 'John'. In the past it was specifically applied to Scottish sailors and, later, soldiers.

[Quizmonster]

A by-form rather than a by-word I should have said above. Its significance is that it means "any bloke" in much the same way as Del-Boy often referred to strangers as 'John'.

[hopalong]

Is it not anything to do with jock straps?

[Quizmonster]

Only in the USA, Hopalong! There, a 'jock' is an athletic type...Scotsmen don't appreciate strapping!