I have a "Särna" chair. "Sarna" in Spanish is "Scabies".
Fun fact: Although "Sarna" comes from Latin, seems like it's only used in Romance languages present in the Iberian Peninsula (Galician, Catalan, Portuguese, Spanish...) and not for example in Italian, Romanian or French, as it's an Iberian loan word. Most other languages derive from another different Latin word, "scabiēs".
The source of the word is almost certainly the Swedish town Särna in this case. Note that ä is not an a, in sound it's more similar to e than a, although it is distinct from both.
Fun fact: Although "Sarna" comes from Latin, seems like it's only used in Romance languages present in the Iberian Peninsula (Galician, Catalan, Portuguese, Spanish...) and not for example in Italian, Romanian or French, as it's an Iberian loan word. Most other languages derive from another different Latin word, "scabiēs".