köken: From ماز (mâz, “oak gall”) + زریون (zaryun, “green, fresh”, literally “gold-coloured”), a dvandva after the berries and leaves of the plant, probably borrowed from another Iranian language as the second part of the compound is of restricted, literary use.
köken: From Proto-Finnic [Term?] (compare Estonian näsi- in näsiniin), possibly borrowed from Proto-Germanic *natją (compare Gothic 𐌽𐌰𐍄𐌹 (nati)). The semantic development would be "net" > "bast" (which was used to make nets) > "mezereon".