from the GNU version of the Collaborative International Dictionary of English
- n. An extravagant fiction embodying an account of some marvelous exploit or adventure.
from The Century Dictionary and Cyclopedia
- n. A disposition to indulge in extravagant romance and wild exaggeration, in the manner of Baron Munchausen, the hero of a work of fiction originally composed by Rudolph Erich Raspe (1737–94), a German scholar and adventurer, whose work, written in English, and published in England in 1785, was afterward expanded by booksellers' hacks, and became very popular.
- n. A grossly exaggerated story or statement such as those of Baron Munchausen; an incredible tale; a ‘whopping’ lie.
Sorry, no etymologies found.
Audubon as we do, we can hardly realize that a well-read and accomplished scholar should suggest the possibility of his veracious description being munchausenism.