Squarehead is a late 19th century ethnic slur directed at German and Scandinavian immigrants. The phrase is meant quite literally as a disparaging reference to the cranial features, though often just used as a generic ethnic slur against those groups.

Basically the stereotypical shape of a Northern European's head was thought to be square- so it was (and is) an insult to call someone with that ethnic makeup squarehead.

Ben Lawrence

Contrary to other beliefs, Square Head is not a reference to the WWII helmets that the Germans used. It is used in reference to the common shape in which many Germans heads are shaped. Dominating brow bones and a square jaw are what create this square look.

A square head is pretty much what it sounds like- a person or thing with a square head.

Having a non existence jawline

1. In the 'olden days,' some Scandinavians were condidered -- by some Americans of the time -- as beleiving what was told them, being rather naive in worldly matters and being somewhat easily conned and deceived -- and consequently, were occasionally referred to as 'squareheads.'

2. A late 19th century ethnic slur directed at German and Scandinavian immigrants to North America.

A literally translated derogatory term used by French-Canadians to describe English-Canadians. But always spoken/written in it's French form. Can be used in a good natured way between friends. Kind of the opposite of "Frog".
Most English-Canadians are unaware of it's usage.

Origin unknown.