1) The small particles separated from grain in the milling process.
1320-1 Pro xvij bus. de dust’ emptis de bovaria, Bolton Priory
1574 an arke called a dustarke, Hipperholme
1621 One olde duste arke 6s 8d
in duste 3s 4d, Slaidburn
1684 one trough to put dust in ... one dustin sieve, Whitley
1739 dusting sieves, Riddlesden.
2) Finely-sifted soil.
Charcoal burners covered the wood that was to be ‘coaled’ in a way that excluded the air and prevented combustion. This might be done with sods, grass, bracken and the like but one component was finely-sifted soil, called ‘dust’ in wood leases: 1672 libertye to … get sods Turfes & dust in the said wood,/i>, Tong
1763 to make Charcoal pitts & Burn the said cordwood & to get Dust & Cover for the said Charcoal pitts in the most proper part of the said Woods, Esholt.