The United States Supreme Court recently began its new term. The first item on its docket has been deciding the cases it will put on its docket. This docket, it turns out, is a low word in a high place–etymologically, that is.

Docket
In the 15th century, a docket was a “summary,” much like the minutes of a meeting–and quite the royal one, if we consider the first appearance of the word as doggette in 1483. Over the next 100 years, it signified an “abstract,” especially for contents of letters patent. By the 17th century, we have evidence for docket‘s use as a memorandum for legal judgements in Samuel Pepys’ famed Diary, an important primary source for the period of the English Restoration–and, for lexicographers, the language of the time. Yet it is by 1790 that we arrive at its usage most familiar to American English ears, namely, a list of cases for trials, spelled, though, as docquet. Of course, a docket lives on today in British English as a label listing out the contents of a package or delivery. And outside of the courts, American speakers may speak of dockets as their to-do lists.
I think we can easily see the legal tale of docket, and thanks to the Oxford English Dictionary (OED) for it. But its etymology tells a very different kind of tale: quite literally, a horse’s tail. Or what remains of it.
Ultimately, etymologists cannot speak to the origin of docket with any final certainty. However, many converge on the same possibility: The core of docket is comprised of dock, in the sense of the “solid fleshy part of a horse’s tail” (OED). In particular, a dock–and its derivate verb “to cut off” or “curtail”–was the remaining stump when a tail was cut short, especially a horse’s tail, to ensure it did not catch in a harness. This practice is perhaps most familiar–and controversial–today with respect to dogs like Boxers.
How, then, do we go from horses to courts? Sorry Caligula, but Skeat sums it up, revealing that old etymological process of metaphor at work: “Apparently allied to the verb dock, to clip, curtail, hence to make a brief abstract.”
This dock–dok, in its earliest form around 1400–is probably from a common Germanic root, which the Oxford Dictionary of English Etymology proposes means “something round” or a “bundle.” Various Germanic languages use the root to refer to “dolls” and “girls.” I suppose we should imagine a doll as a small bundle, perhaps swaddled in clothes or a blanket, or perhaps as made of straw.
To dock someone’s pay is attested in 1822 and is so derived.
“-Et” Cetera
With dock clipped off, what of docket’s –et? It may be a variation on -ed, which forms the past tense and past participial forms of regular English verbs, and whose sound (and spelling) will vary depending on its environment.
Or it could be a visitor we’ve seen around these parts quite a bit recently (cf. target, gobbet, and, in its Italian cousin, rocket): the French diminutive -et. This form is used for masculine nouns in French and is featured in not a few everyday words. As in your new iPhone 6, whose tablet-like size renders your pocket useless. The feminine form is probably more recognizably French: -ette, like baguette. You may know its Italian counterpart in bruschetta or libretto, its Spanish iteration in señorita or Juanito.
The diminutive suffix surfaces, too, in Ernest Weekley’s alternative etymology of docket, which, according to my research, stands alone. He jumps off from the earliest attestation of doggette, seeing in it the Italian doghetta, a “bendlet in heraldry,” half the width of a so-called diagonal band on a shield. This doghetta, Weekley continues, is a diminutive of doga, a “cask stave.” He points us to label (also originating in heraldry as a kind of strip) and schedule (going back to strips of paper used in ancient Rome) for the sense evolution. A cask stave, then, supposedly resembles a heraldic band that evokes a strip of paper on which one would have recorded a docket.
Dock may make a stronger case than doga, but some word origins will never meet with final judgment.