Nonce is from Middle English for pan anes - for the occasion - which became pe nanes (as a newt replaced an ewt). Johnson moots the German nutz (need) and discounts the Old French noisance (nuisance, mischief). Between the 16th and 19th centuries, it meant both for the occasion and temporarily - the latter has gained ascendancy, for now.
AT THE start of I & Claudius Clare de Vries is yet to motor across America with her old cat, but still here, is "lying in bed, ermintruminating over my life". Does this echo Ermyntrude the cow in The Magic Roundabout or - with added r - the artist whose bed, a former free-for-all, is now closely guarded at the Tate? But ermine betokens purity. Ermintruminate, unlike the book itself, will stay a nonce.