Nun*cu”pa*to*ry\, a. Nuncupative; oral.

nun·cu·pa·tive /ˈnʌŋkyəˌpeɪtɪv, nʌŋˈkyupətɪv/

(esp. of a will) oral; not written.

1540–50; < ML ( testāmentum ) nuncupātīvum oral (will), neut. of LL nuncupātīvus so-called, nominal, equiv. to L nuncupāt ( us ) ptp. of nuncupāre to state formally, utter the name of (prob. < *nōmicupāre, deriv. of *nōmiceps one taking a name, equiv. to *nōmi– comb. form of nōmen name + –ceps taking, possessing; see prince) + –īvus -ive


“Quite right, sir, and while the subject is fresh in my mind, I would like you to resolve a perplexity. A single father often boasts four sons, but how does a single son boast four fathers?”

Disserl, Vasker and Archimbaust rapidly tapped the table; the eye ear and arm were interchanged. At last Vasker made a curt gesture. “The question is nuncupatory.”

Source: Tales of the Dying Earth by Jack Vance.

The use of this word appears to be a mistake or malapropism on the part of the character.