Good manners are named after a label.
World Wide Words traces the French word back to Old French estiquette, linked to a verb meaning to press, pierce, insert or attach. Etymonline traces that verb to Frankish stikkan, "to stick," while World Wide Words adds that it may be linked to Latin stilus. The first sense was apparently a post set in the ground. Posts often carried signs, so the word came to mean a label. Later it meant a lawyer's bag listing the papers for a trial, then any ticket, such as a price tag.
The court sense came next. World Wide Words says the word was used at the Burgundian court of Philippe the Good for the court's schedule, though it dates that use loosely. It later meant court ceremonial, especially at Versailles, and then a general code of polite behavior. Etymonline dates the English word to 1750, borrowed from French. Wikipedia credits Lord Chesterfield's letters to his son, published in 1774, with the first modern English use.
A popular story says small cards of instructions were handed to courtiers at Versailles under Louis XIV. Etymonline says only that the French sense "may come from" such cards. World Wide Words does not mention them, and Wikipedia does not either. Wikipedia does say that Louis XIV used codified etiquette to control the nobility and assert his power as an absolute monarch. The cards may be a tidy way to explain the shift from "label" to "rules," but they are unproven.
The word also has a twin. World Wide Words says English dropped the initial es from estiquette earlier, making ticket, which Etymonline dates to the 1520s. So a ticket to the theater and a lesson in table manners are the same French word, borrowed twice.
French has borrowed back. World Wide Words notes that modern French took ticket from English for a bus or subway ticket, and label for a seal of approval.