Scholars think
Jasm derives from or is a variant of slang
jism or
gism, which the
Historical Dictionary of American Slang dates to 1842 and defines as "spirit; energy; spunk."
Jism also means semen or sperm, the meaning that predominates today, making
jism a
taboo word. Deepening the nexus among these words is the fact that "spunk" is also a slang term for semen, and that "spunk"—like jism/jasm—also means spirit, energy, or courage (for example: "She showed a lot of spunk.") In the 19th and early 20th centuries, however,
jism was still used in polite contexts.
Jism, or its variant
jizz (which, however, is not attested in the
Historical Dictionary of American Slang until 1941), has also been suggested as a direct source for
jazz. A direct derivation from
jism is phonologically unlikely.
Jasm itself would be, according to this assumption, the intermediary form.