Part of this practice may have been rooted in an older folk culture of fans.
Wrai Ballard, then editor of the Spectator Amateur Press Society refused to publish it for fear that the article's bawdy content could get them into trouble with the Post Office under the Comstock Laws, but found the typo itself amusing, and mentioned it repeatedly; thus, Jacobs' typo became the self-identified term for the genre/subculture while it was still an informal, unrecognized activity at conventions.
Its first documented deliberate use was by Karen Anderson in Die Zeitschrift für vollständigen Unsinn (The Journal for Utter Nonsense) #774 (June 1953), for a song written by her husband Poul Anderson.
It's 2018 And people still falling for these scammer/Catfish...
BP Need to step it up and so we can expose these frauds..
The term derives from the word "morose", as in "ose, morose, even-more-ose".
A further variant is "cheeri-ose": ose songs to cheery tunes, or treating such a subject lightheartedly; cf. For the first few decades of the occasional science fiction convention, there had been late-night singing sessions in hotel rooms.
A significant number of filk songs are parodies, whether in the original sense of simply re-using a tune or in the modern sense of specifically humorous re-use.
Some are parodies of songs from popular culture, others are parodies of existing filk songs.
Such topics include songs about cats, popular culture, and politics.