1) Of uncertain origin, but probably high quality iron from Sweden. Later it came to be used more generally for iron from a number of countries, imported via the Baltic.
It is known that Sheffield cutlers were using iron and steel imported from other countries from the sixteenth century at least, and much of it came via Danzig. In fact iron had been imported into Yorkshire from a much earlier date, and the key to that is in the word ‘osmund’ which has an uncertain origin but referred initially to high quality iron from Sweden: the term later came to be used more generally for iron from a number of countries, imported via the Baltic. It was imported as small bars or rods, and the OED notes examples from 1280, with one for Hull in 1400-12. In York, a case in 1428 against John Lyllyng proved that he had forged fals osmundes by mixing tin and lead: William Kyam saw ij barells of osmundes market with John Lilling’s mark. The published customs accounts for Hull contain numerous references, starting with a cargo from Danzig brought in the Jacob: 1453 1 last’ osmondes: an editorial note says that a ‘last’ was 12 barrels of osmunds. In the same period there are entries for iron imported into Hull from Germany, Hungary, Liege [lukys], Scotland and Spain.