In a square shape or position; set or positioned at right angles.
From a- (on, in, at) + square, another example of the 'a-' prefix used to indicate a state or position. This follows the same archaic English pattern seen in 'aslant' or 'askew,' where 'a-' marked adjectives describing spatial orientation.
Words with the 'a-' positional prefix like 'asquare,' 'askew,' and 'aslant' reveal how English once had a rich system for describing how things were positioned—most of these have been replaced by their simpler forms ('square,' 'skew,' 'slant'), but a few stubbornly survived in dialects.
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