Evan Morris over at The Word Detective, answering a similar query, has some helpful musings.
He argues that despite all the good lemons have done, they've suffered from an image problem since the dawn of their cultivation—due primarily to their stinging acidity and tough skins.
He continues,
The word “lemon” comes to us from the Old French “limon,” which was derived from Arabic roots and served as a generic term for citrus fruit in general (which explains how the same root could also give us “lime”). The use of “lemon” to mean “disappointing result” or “something unwanted” is very old, reflecting the fact that, while useful in cooking, a lemon standing alone is just a lump of sourness with a tough skin to boot. In Shakespeare’s play Love’s Labours Lost (1598), for instance, one character proclaims, “The armipotent Mars, of lances the almighty, Gave Hector a gift …,” to which another puckishly suggests, “A lemon.”
And, clearly drawing from some of the OED citations mentioned by @Barrie, he concludes,
In the mid-19th century, “lemon” was used as a colloquial term for a person of a “tart” disposition, as well as, more significantly for our purposes, slang for a “sucker” or “loser,” a dim person easily taken advantage of. It has been suggested that this latter use stems from the idea that it is easy to “suck or squeeze the juice out of” such a person (“I don’t know why it is, rich men’s sons are always the worst lemons in creation,” P.G. Wodehouse, 1931). By 1909, “lemon” was also firmly established in American slang as a term for “something worthless,” especially a broken or useless item fobbed off on an unsuspecting customer.
It’s likely that the current use of “lemon” to mean “something that doesn’t live up to its billing” or “a disappointing purchase” comes from a combination of “lemon” in the “sucker” sense (i.e., the buyer got “taken”) and the much older sense of “lemon” meaning “something undesirable.”
Also of note, I found occasional use of the phrase (at least as early as 1918), "to give someone a lemon and pass it off as a nugget (of gold)." If this was the original saying, later shortened to "handing someone a lemon," then the implication of trickery is confirmed and the metaphorical use of lemon further explained.
The OED's first citation for "bullet point" (in an online draft addition) is in 1983:
1983 Datamation Sept. 221/1 Each chapter concludes with a bullet-point list of ‘things to think about’ or ‘things to remember’, which is particularly helpful if it's been a few days between chapters.
The term "bullet point" originally seems to have meant not the typographical symbol, but the text marked by the bullet symbol • in a list. That is, a bullet-point list is a list of points you are making in a presentation. For example, a Harvard Graphics manual (the predecessor of PowerPoint) in 1990 says:
Pressing Enter a third time creates the first bullet point and places the cursor to the right of the bullet.
However, the term "bullet point" was very quickly transferred to mean the symbol as well.
I have a theory of when and why bullet points were introduced, but absolutely no confirmation.
Looking through 19th century books, I can't find any bulleted lists. Lists are either indexed by numbers, or items are identified with spacing and indentation. When typewriters started being widely used in the early part of the 20th century, people started preparing typed documents with less care than they had taken with printed materials, and it was too much trouble to renumber lists while editing documents. So they started using asterisks instead of numbers. Printers took these lists marked by asterisks and used typographical bullet symbols instead.
Best Answer
The earliest match I could find for "triple threat" is from "Cry of Calamity," in the Marietta [Ohio] Daily Leader (September 16, 1900):
Here "triple threat" seems to mean simply "three-part danger." The next batch of matches involve chess, as exemplified by the 1907 example cited in deadrat's answer.
The sports examples first appear in 1916–1919, and all three mentions from this period involve U.S. football. From "Football," in the Oklahoma City [Oklahoma] Times (November 16, 1916):
From "Developed Men Needed," in the Richmond [Virginia] Times-Dispatch (March 5, 1917), quoting "E.B. Cochems, once mentor of the St. Louis University team, and a constructive coach":
And from "High Lights and Shadows in All Spheres of Sport," in The [New York City] Sun (November 11, 1919):
It appears from these descriptions that kicking was a weapon because U.S. football still resembled rugby far more than it does today, with kicking serving as a way to move the ball quickly downfield. One very interesting source in that turns up in a Google Books search is a retrospective discussion of U.S. football going back to the 1880s. From Neilson Poe, "The Forward Pass," in Leslie's Illustrated Weekly (November 12, 1921):
According to this source, the forward pass became legal in U.S. collegiate football in 1906, meaning that there was no possibility of "triple threat" being applied to the sport before that year. From these instances, it appears that "triple threat" entered the sports lexicon through U.S. football, perhaps independently of its use in chess or perhaps influenced by that use. In any event, the notion of a "triple threat" consisting of three dangerous things seems to have existed—before either the football usage or the chess usage emerged—as a political idea, at least in Marietta, Ohio.