The story
From the German name Münchhausen, after the fantastical tales related by the fictional Baron Munchausen (sic) in Rudolf Erich Raspe's English-language novel Baron Munchausen's Narrative of His Marvellous Travels and Campaigns in Russia (1785). The character was loosely based on Baron Hieronymus Karl Friedrich von Münchhausen (1720–1797).
Etymology from Wiktionary, CC BY-SA 4.0.