Classifications of fairies
The fairies of Irish, English, Scottish and Welsh folklore have been classified in a variety of ways. Two of the most prominent categories, derived from Scottish folklore, are the division into the Seelie Court and the Unseelie Court. These categories may reflect an earlier (medieval) classification of the Germanic elves of light and darkness (Ljósálfar and Dökkálfar), as the corresponding Insular Celtic "fair folk" do not appear to have a comparable division. William Butler Yeats, in "Irish Fairy and Folk Tales", further divided them into the Trooping Fairies (appearing in splendid processions known as fairy rades) and  the Solitary Fairies (mischievous spirits appearing on their own). Katharine Mary Briggs noted that a third distinction might be needed for "domesticated fairies" who live in human households (see household spirit). Seelie and Unseelie. Etymology. The Northern and Middle English word (also , , , and "seely"), and the Scots form , meaning "happy", "lucky" or "blessed" and meaning "unhappy", "misfortunate" or "unholy" are derived from the Old English and . The Modern Standard English word "silly" is also derived from this root and the term "seely" is recorded in numerous works of Middle English literature such as those by Geoffrey Chaucer. Many ballads and  tales tell of "Seilie wichts", a Lowland Scots term for fairies. In Wales there were said to be two fairies or elves called "Silly Frit" and "Sili go Dwt" whose names represent a borrowing of the adjective "silly" (in this case meaning "happy") as applied to fantastical beings from its usage on the English marches bordering Wales rather than the Anglo-Scottish border. The former name is purely English while the latter is a corruption of English fairy names featuring ""tot"" (such as Tom Tit Tot) as an element. Seelie and Unseelie Courts. In Scottish folklore, faeries are divided into  the "Seelie Court" (more benevolent, but still dangerous) and the "Unseelie Court" (more malevolent). The Seelie Court were described as those fairies who would seek help from humans, warn those who have accidentally offended them, and return human kindness with favors of their own. Still, a fairy belonging to this court would avenge insults and could be prone to mischief. The Unseelie Court, conversely, was used to describe the darkly-inclined fairies. Unlike the Seelie Court, no offense was deemed necessary to bring down their assaults. As a group (or "host"), they were thought to appear at night and assault  travelers, often carrying them through the air, beating them, and forcing them to commit such acts as shooting at cattle. In Scotland, they were seen as closely allied with witches. Some of the most common characters in the Unseelie Court were bogies, bogles, boggarts, abbey lubbers and buttery spirits. In other cultures. The division into "Seelie" and "Unseelie" spirits was roughly equivalent to the division of Elves in Norse mythology into "light" and "dark" distinctions. In the French fairy tales as told by the "précieuses", fairies are likewise divided into good and evil, but the effect is clearly literary. Many  of these literary fairies seem preoccupied with the character of the humans they encounter. The Welsh fairies, "Tylwyth Teg", and the Irish "Aos Sí" are usually not classified as wholly good or wholly evil. Modern fairies. W.B. Yeats divided fairies into the solitary and trooping fairies, as did James Macdougall in "Folk Tales and Fairy Lore". Katharine Mary Briggs noted that a third distinction might be needed for "domesticated fairies" who live in human households. Trooping. These fairies contain the aristocracy of the fairy world, including the Irish Aos Sí. They are known as trooping faeries because they travel in  long processions, such as the one from which Tam Lin was rescued. But the trooping fairies also include other fairies of lesser importance; a trooping fairy can be large or small, friendly or sinister. Solitary. These fairies live alone and are inclined to be wicked and malicious creatures, except for beings such as the brownie who is said to help with household chores. Domesticated. These fairies generally function as pets or servants of the households they live in, but sometimes might temporarily join with other fairies for merry-making activities. Welsh fairies. The folklorist Wirt Sikes formally divided Welsh fairies , or Tylwyth Teg, into five general types. They include the Ellyllon (elves), the Bwbachod (household spirits similar to brownies and hobgoblins), the Coblynau (spirits of the mines), the Gwragedd Annwn (lake maidens), and the Gwyllion (mountain spirits resembling hags). Sikes acknowledged that while such classifications are largely arbitrary, "the student of folklore must classify his materials distinctly in some understandable fashion, or go daft."