Dear Word Detective: Found your column on “gams” and “door jambs,” but it didn’t speak to the many-faceted “jam/jamb.” Is a traffic “jamb/jam” related to the door or the jelly? Is something “jambed up” or “jammed up”? What does a musical “jam session” have to do with either the door jamb or the jelly-jam (if anything?) Are the various “jamb/jams” from the same root or do they have different variations? Please help as I’m stuck — or all jammed up. — Barney Johnson.
This question is making me hungry, probably because I eat a lot of peanut butter and jelly sandwiches (though usually with jam or preserves), often for breakfast. Hey, it beats microwave pancakes, and no, I cannot cook “real food” when I’m asleep. But how come a teeny-tiny jar of raspberry preserves now costs $4.50? It’s not even organic! And it’s probably 50% high-fructose corn syrup! (Excuse me, the TV says we’re supposed to call that “corn sugar” now. Yum!) And I’m running out of exclamation points! Anyway, it’s an outrage, so please write your local politician. And while you’re at it, tell those darn kids to get off my lawn.
That’s a rather tangled web you’ve woven in your question, so I’m going to jump to the finish line right now, which should help untie a few knots. No, there is no connection between “gams” (slang for legs) and “jamb” (door frame) on the one hand, and the various permutations of “jam” (traffic, musical, jelly-jam, etc.) on the other.
As I said in that column a couple of years ago, “gams” as slang for a woman’s legs dates back to the late 18th century, when it applied to the legs of either sex. The root of “gam” may be the Italian “gamba,” also meaning “leg,” but it may also have come from a close cousin of “gamba,” the French “gambe” or “jambe,” which gave us the “jamb” found in “door jamb,” the side pieces of a door frame. This “jamb” is so-called because it is the “legs” which support the frame.
“Jam” first appeared in the early 18th century as a transitive verb meaning “to press or squeeze something” or “to wedge or immobilize something in an opening” (“The Ship … stuck fast, jaum’d in between two Rocks,” Defoe, Robinson Crusoe, 1719). The origin of “jam” is a bit hazy; the Oxford English Dictionary (OED) labels it “apparently onomatopoeic” and suggests it might be a variant of the verb “to champ,” meaning “to chew or bite” (as a horse noisily “champs” on its bit when excited or impatient). So “jam” was intended to be evocative of the sound, sight or feeling of something being forced into a tight spot.
“Jam” as a verb went on to mean “to block or obstruct” (eventually producing the “jamming” that can block radio signals) and, as an intransitive verb, meaning “to become immovable or unworkable by wedging or sticking” as a gun may “jam.” As a noun, “jam” developed a variety of meanings, most of them involving either the act of “jamming” or the result of “jamming,” as in a “traffic jam” or, in a figurative sense, “jam” meaning a difficult situation (“I’m in a jam. But I’m not going to the cleaners… Half of this money is mine,” Raymond Chandler, 1950).
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.