bǫrkr

Old Norse bǫrkr, meaning the outer covering of a tree, entered English during the Viking period and largely displaced the native Old English word rind for this meaning. (English kept 'rind' for fruit peels and cheese coatings.) The Norse word has no established connection to the Proto-Indo-European root — it may be a specifically Germanic innovation. Tree bark was not just a plant feature to the Norse; it was a technology. Birch bark was used for writing, roofing, waterproofing boats, and making containers across Scandinavia and the North.

Bark cloth — made by beating the inner bark of trees, particularly the paper mulberry — is one of the oldest textile technologies in the world, predating woven cloth. Polynesian tapa cloth, Central African barkcloth from Uganda (declared a UNESCO Intangible Cultural Heritage in 2008), and South American bark textiles all developed independently. The tree's skin became human clothing on at least three continents without contact between the cultures. The material was obvious. The technique was convergent.

The other English barks are unrelated. 'Bark' meaning a dog's vocalization comes from Old English beorcan and is onomatopoeic. 'Bark' or 'barque' meaning a sailing vessel comes from Latin barca, possibly from Egyptian. English acquired three unrelated words, spelled them all the same way, and kept them. This is called homography, and English is full of it, but bark is one of the more extreme cases — plant, animal, and vehicle sharing four letters.

Quinine, the first effective antimalarial drug, was extracted from the bark of the cinchona tree. Aspirin was derived from salicylic acid, found in willow bark. Cork is the bark of the cork oak. Cinnamon is the bark of the Cinnamomum tree. Bark — the tree's protective outer layer — has provided more medicines, materials, and spices than most people realize. The outer covering that the Norse named is the tree's most useful part for humans.