The name gossan appears to come from Cornish miner's slang.2 The terms "iron cap" and "iron hat", common in America,3 are direct translations from the German "Eiserner Hut" or "Eisenhut", which term was also used in America.4
Johnson, Joseph Colin Francis (1897) Getting Gold: A Practical Treatise for Prospectors, Miners, and Students Lippincott, Philadelphia, Pennsylvania, page 15, OCLC 5164023 https://books.google.com/books?id=Z-oxAQAAMAAJ&pg=PA15 ↩
"gossan" Century Dictionary and Cyclopedia Vol. III, page 2581 /wiki/Century_Dictionary_and_Cyclopedia ↩