In an athwart or transverse direction; across something from side to side.
Combination of 'athwart' (Old English æt hwærf) with the suffix '-wise' (Old English wīsan, 'manner or direction'), creating an adverb meaning 'in the athwart manner.'
The suffix '-wise' is ancient—we still use it in 'clockwise' and 'otherwise'—and sailors stacked it onto 'athwart' to create yet another way to say 'sideways across the ship,' showing how maritime communities densified their directional vocabulary.
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