From Twelfth Night (1.5):
Wit, an’t be thy will, put me into good fooling!
Those wits, that think they have thee, do very oft
prove fools; and I, that am sure I lack thee, may
pass for a wise man: for what says Quinapalus?
‘Better a witty fool, than a foolish wit.’
The Arden note says:
An invented Latin authority, probably inspired – given the context of rhetorical and logical discussion (cf. syllogism, 46) – by Quintilian(us), author of the Institutio Oratoria, a book much studied in Elizabethan schools and universities. This allusion may be ‘contaminated’ by another Latin auctoritas, Apuleius, author of The Golden Ass, and by the name of the Roman coin quinarius or quinary, worth five bronze ‘asses’ and bearing the type of the victoriate, whose ‘weight standard had come from Illyria.’ Shakespeare seems to be imitating Rabelais’ pseudo-pedantic way with invented auctoritates. In any case, as Mahood observes, ‘this no longer gets a laugh.’
The pseudo authority feels right but I’ll add another comically farfetched possibility that just occurred to me. Continuing the Latin theme of the Arden note, start with the definition of the word palus in Lewis and Short:
I Lit. (very freq. and class.; syn.: sudes, stipes): ut figam palum in parietem, Plaut. Mil. 4, 4, 4; id. Men. 2, 3, 53: damnati ad supplicium traditi, ad palum alligati, Cic. Verr. 2, 5, 5, § 11: palis adjungere vitem, Tib. 1, 8 (7), 33; Ov. F. 1, 665: palos et ridicas dolare, Col. 11, 2, 11; Varr. 1. 1.—The Roman soldiers learned to fight by attacking a stake set in the ground, Veg. Mil. 1, 11; 2, 23; hence, aut quis non vidit vulnera pali? Juv. 6, 246.—And, transf.: exerceamur ad palum: et, ne imparatos fortuna deprehendat, fiat nobis paupertas familiaris, Sen. Ep. 18, 6.—In the lang. of gladiators, palus primus or palusprimus (called also machaera Herculeana, Capitol. Pert. 8), a gladiator’s sword of wood, borne by the secutores, whence their leader was also called primus palus, Lampr. Commod. 15; Inscr. Marin. Fratr. Arv. p. 694.—Prov.: quasi palo pectus tundor, of one astonished, stunned, Plaut. Rud. 5, 2, 2.—
II Transf., = membrum virile, Hor. S. 1, 8, 5.
The element I want is option 2, the unique transferred meaning of membrum virile. The single passage is from Horace’s Satires and quoted below:
Once I was a fig-wood stem, a worthless log, when the carpenter, doubtful whether to make a stool or a Priapus, chose that I be a god. A god, then, I became, of thieves and birds the special terror; for thieves my right hand keeps in check, and this red stake, protruding from unsightly groin…..
Olim truncus eram ficulnus, inutile lignum,cum faber, incertus scamnum faceretne Priapum,maluit esse deum. deus inde ego, furum aviumque maxima formido; nam fures dextra coercet obscenoque ruber porrectus ab inguine palus;…..
The English disguises this but the narrating Priapus describes itself as possessed of an ‘ab inguine palus‘ – which produces a sound sequence ‘guinepalus‘ terribly close to Shakespeare’s ‘quinapalus.’ Which would then turn the reference to a learned but bawdy citation of his own dick as his source of wisdom. I have now proven the undesirability of a foolish wit.