The noun boot, meaning “a covering for the foot and lower part of the leg,” has been in the language since the early 14th century. The word existed in medieval Latin and entered English via French.
The popularity of boots as footwear has never diminished, but our use of the word boot and similar forms doesn’t always pertain to the article of apparel.
First let’s look at terms and expressions that do relate to footwear.
bootleg: As a noun, bootleg is recorded in the 17th century with the meaning “the leg of a boot.” Nineteenth century American frontiersmen favored bootlegs as convenient places to carry knives and shooting irons. The term acquired its present associations with the illicit trading of liquor even before Prohibition became the law of the land in 1920; a handful of states outlawed alcoholic beverages earlier. For example, Kansas banned alcohol in 1881. A bootleg could conceal a small bottle of liquor.
In current usage, bootleg denotes anything that is traded or trafficked illicitly: bootleg CDs, bootleg diamonds, bootleg babies, etc. As a verb, bootleg means “to traffic illicitly in liquor or anything else.” The verb bootleg is also an American football term meaning “to carry the ball deceptively.”
bootstrap: as a noun, a bootstrap is a loop attached to the top of a boot to help the wearer pull on the boot. I’ve written about the figurative meanings of bootstrap here.
boot camp: This is a term for U.S. Marine and Navy recruit training. The term boot as slang for recruit may date from the Spanish-American War. U.S. sailors wore leggings called boots and the term transferred to the sailors themselves. By extension, boot camp is now also used for any training camp or program that resembles boot camp by requiring rigorous training. The term can also refer specifically to a facility or program for juvenile offenders who are forced to follow a rigidly structured routine of drill and discipline.
bootlicker: A cringing, favor-seeking toady is called a bootlicker: a person who would do any demeaning thing to please and flatter a person in power. You can find more terms for subservient people here.
jackboot: a type of large, strong cavalry boot popular in the 17th and 18th centuries was called a jackboot; later it was worn by German military and paramilitary units during the Nazi regime. Even before its association with the Nazis, the term had acquired the connotation of military oppression.
boot: As a verb, “to boot” can mean “to kick,” as in “They booted out the old superintendent and hired a new one.” As a verb in the context of computer use, boot derives from bootstrap.
to boot: We still use the expression “to boot” with the meaning “in addition” or “as a bonus”:
The guy’s a chronic complainer and a tightwad to boot.
The most patient and behaved dog in the world (and she’s Irish to boot).
We offer inexpensive prices for our AC and heating units and we will throw in a free thermostat to boot!
The expression “to boot” comes from an obsolete noun boot, meaning “good, profit, advantage.” The related verb boot meant “to make better, to remedy.” You may have encountered the verb boot in Shakespeare:
It shall scarce boot me
To say “Not guilty.” Hermione, A Winter’s Tale, III.ii.24.
booty: As a noun meaning “plunder, gain, profit,” booty comes from an Old French word, butin.
As a noun meaning “a woman’s body (or a part thereof) as a sex object,” booty originated as 1920s black slang, possibly an alteration of another slang word, botty, meaning bottom or buttocks.