This is a strange blunder. A napperon , converted into An apperon. “Napperon” is French for a napkin, from nappe (cloth in general). Halliwell, in his Archaic Dictionary, p. 571, gives Nappern (an apron) North.
Other examples of n attached to the following noun, or detached from it, are an adder for a nadder (Old English, noeddre); a newt for an ewt; a nag (Danish, ög ); nuncle (Shakespeare), mine uncle; For the nonce (this once), where n is transferred from the preceding pronoun tha-n or the-n, i.e. this-n (accusative case after “for”).