I was curious about the etymology of the word "Jam". Here's a little snippet of an article I found. http://www.word-detective.com/2011/09/jam/ --Snip-- The use of “jam” to mean “A conserve of fruit prepared by boiling it with sugar to a pulp” (OED), which first appeared in the 18th century, is considered a separate word from “jam” in the “blockage” sense. But it’s very likely that this jelly-esque “jam” took its name from the crushing or squeezing of fruit to make it, reflecting the original “press or squeeze” sense of the verb “to jam.” Now that we have all those little ducks in at least a ragged row, it’s time to face the giant monster duck in the room: no one knows for sure why an improvisational performance or informal session by a musical group is called a “jam session.” This usage, which dates back to the 1920s jazz scene, may be using the “pile on” or “pressure” sense of “jam” to describe the effect of many musicians playing together without a score. Or it may be invoking the use of “jam” in the “jelly” sense to mean “something sweet; a very nice treat,” a usage that dates back to the 19th century (“Without Real Jam — cash and kisses — this world is a bitterish pill,” Punch, 1885). I tend to think this “sweet treat” sense of “jam” is more likely to have been the source of “jam” in the musical world, given that we are taking about the slang of musicians, to whom a “jam” represents a welcome opportunity for self-expression.