The closest predecessor to this entry is Etymologicum Gudianum 510.5-6, though different parts of it appear in various forms in other lexica. Ultimate sources are scholia and commentary on Homer, Iliad 5.725 (web address 1), where the neuter plural headword occurs.
Sometimes forms of the word appear without the double-s (e)pi/swtr-), but the double-s is metrically necessary in Homer.
2Similar descriptions are found in many sources (e.g. scholia; Herodian 3.2.509.15-16; Apollonius Sophistes, Homeric Lexicon 74.8; Hesychius epsilon5221; Etymologicum Gudianum 510.7, Etymologicum Magnum 364.26), though in the Homeric passage in question the rims are said explicitly to be of bronze.