In a direction or manner that crosses something; diagonally or perpendicularly across.
From 'crossway' (noun) with adverbial '-s' ending, common in Middle English formation. Alternatively from 'cross' (verb) combined with '-ways' suffix meaning 'in the manner of'.
The phrase 'going crossways' appears in folk remedies and superstitions throughout Europe—there's something deeply intuitive about how humans perceive diagonal motion as unusual or even transgressive, which is why many traditional warnings tell you never to go 'crossways' through a field at night.
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