rodomontade

I really like this word, the way it rolls off the tongue:

rodomontade n extravagant boasting vi to bluster or brag [Origin from the boasting of Rodomonte in Ariosto's Orlando Furioso] Chambers, 1998

It's another word originating from a work of creative writing, like mumpsimus, and actually I think the two of them make a nice pair: "Have you heard Bob's latest rodomontade?" "Oh, he's just an old mumpsimus" etc.

As to the word's origins, Ariosto was an Italian poet who wrote the romantic epic poem Orlando Furioso in c.1513. Rodomonte is a boastful warrior who joins forces with the King of Africa to overrun Europe. They besiege the Emperor Charlemagne in Paris, but the bulk of the action takes place all over the world in a fantastical love story that even takes a detour to the moon.

"And boastful Rodomont, with vengeful doom,
Gives Paris to the flames, and levels Rome."

(original Italian)
"e Rodomonte audace se gli vanta
arder Parigi e spianar Roma santa."

[from Canto 65, taken from Project Gutenberg]

It's perhaps needless to say that things don't go too well for old Rodomonte. He's cruel, haughty and scornful and the poem ends with his death. Beware boasters: don't get cocky.