Nothing; used in Northern English dialects, especially in Yorkshire and Lancashire, to mean not a single thing.
From Middle English 'no wight,' where 'wight' meant 'creature' or 'person,' literally meaning 'no person/creature.' Over time 'no wight' collapsed into 'nowt.'
Dialectal English has these amazing fossils: 'nowt' preserves the medieval word 'wight' (creature), which survives nowhere else in modern English except in 'wight' compounds.
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