Without a context in the TLL edition the precise sense of this word remains unclear. Latin pervius means ‘that allows passage through’ (DMLBS 2250a). If the Anglo-Norman word is related to percer, a sense similar to the DMLBS’s more figurative ‘(of glass or liquid) that affords passage (to sight), transparent’ may be construed for the negated adjective, i.e. ‘impenetrable, not transparent’. However, in other instances in TLL, the Latin pervia is glossed as ‘avantalable’, which raises the possibility that ‘nonpersable’ may be a scribal or editorial error for ‘nonpassable’ (otherwise not attested in AND², but see nunpassage).