For those who have not clicked on the link, Urban Dictionary quotes it as: "A fair fight, the implication being of no-interference by either sides mates. Heard often on the streets of every town and city in Scotland soon after pubs call last orders."
All my years in Scotland at last orders I never heard it. Suspect that far from "the streets of every town and city in Scotland" it is very much a Glasgow term. Mind, I have heard of a Glasgow kiss.
"Square go ya radge!"
Possibly more authoritative, the Glaswegian Dictionary:
Glaswegian Dictionary - Glasgow Terms and Phrases | Glasgowvant
www.glasgowvant.com
Thought I would throw in a few entries starting with "Square go":
Square go: Someone who is asking you to fight them will ask for a square go. The question would simply be phrased “Square go?!?”
Stoat: If someone is “stoating” they cant walk in a straight line without falling over. This would generally refer to someone who is inebriated.
Stoater: This can either be a very nice looking person, or something very good such as “a stoater of a goal”.
Stooky: A plaster, such as the type on a broken bone in the body.
Swagger: A specific type of walk, tending to be an over-confident and rather manly walk.
Tadger: Male genitals, penis, boabie, willy, wangdoodle, knob, cock, dick, johnson.
I do like that distinction between the verb, "stoat" and the noun, "stoater". It might have something to do with the Weegie appreciation of the state of "stoatism".