Square/Square deal/Square meal etc

To set something square is an expression that dates from the 1400s and means to set something straight. It is a figurative usage of mathematical squareness in that only straight lines or right angles apply. The notion of mathematical squares, of course, had been in use for millennia before this. People had been setting things square since Babylonian times 1900 BC. Out of this notion of squareness or straightness, a number of idioms have evolved like ‘square deal’, ‘fair and square’, ‘all square’, ‘square meal’ etc. Square as both an adjective meaning fair, honest, equitable, and as a verb meaning to act in the same way, date from the late 1500s. ‘Fair and square’, signifying equitable and honourable circumstances dates from the early 1600s, whereas ‘square deal’ is an Americanism that derives from card playing from the late 19th century, but by the early 20th century it was applied to any fair transaction. ‘Square meal’ is also originally American for a full, substantial meal, dating from c.1860. ‘All square’ meaning honours even, everything is alright, scores are level or debts are settled, dates from around the same time. Square in the military sense of a formation of soldiers facing outwards in the shape of a square dates from the late 1500s.