The word is only attested in TLL (where it is relatively common), usually as a gloss to orichalcus (DMLBS 2053c). The AND definition is inferred from the Latin. The etymology of orpetre is unknown, although an association with or¹ is very likely (despite the fact that etymologically orichalcus is unrelated to aurum ('gold'), but derives from the Greek word for brass, ὀρειχαλκος).

The sense of the word as a gloss to Latin fulgetra(TLL i 23.964) remains obscure without any further context; cf. fulgetrum, DMLBS 1024b, defined as ‘a flash of lightning’.