Etymology
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swallowtail (n.)
also swallow-tail, 1540s as a type of arrowhead, from swallow (n.1) + tail (n.). Of a type of butterfly, by 1776; of a type of coat, 1835. As an adjective from 1590s. The bird's tail is long and deeply forked.
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redtail (n.)

also red-tail, 1812 in reference to a type of North American hawk; earlier used of various smaller European birds with red tail feathers (1550s, compare redstart); from red (adj.1) + tail (n.). Related: Red-tailed (c. 1600).

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muggle (n.2)

c. 1200, "a fish-tail," also, apparently, "a person with a fish-tail" (only as a surname), a word of uncertain origin, perhaps from Latin mugil "mullet."

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adulation (n.)

"servile or insincere praise," late 14c., from Old French adulacion, from Latin adulationem (nominative adulatio) "a fawning; flattery, cringing courtesy," noun of action from past-participle stem of adulari "to flatter, fawn upon."

This is usually said to be from ad "to" (see ad-) + a stem meaning "tail," from a PIE *ul- "the tail" (source also of Sanskrit valah "tail-hair," and Lithuanian valai "horse's tail"). The original notion would be "to wag the tail" like a fawning dog (compare Greek sainein "to wag the tail," also "to flatter;" also see wheedle).

But de Vaan finds phonetic problems with these and concludes the etymology is uncertain, though he proposes a connection with avidus "eager," via *adulo- "who is eager toward something," hence "a flatterer." Adulation may proceed from true blind worship or be insincere, from hope of advantage.

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dovetail (n.)

also dove-tail, 1580s, in carpentry, "tenon cut in the form of a reverse wedge," the strongest of all fastenings, from dove (n.) + tail (n.). So called from resemblance of shape in the tenon or mortise of the joints to that of the bird's tail display. As a verb, "to unite by dovetail tenons," 1650s; figuratively "unite closely, as if by dovetails." Related: Dovetailed.

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pintail (n.)

type of duck, 1767, from pin (n.) + tail (n.); so called from the peculiarity of the tail (narrow with long central feathers). In Middle English it is given once (c. 1300) as an epithet for the hare.

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yellowtail (n.)
type of fish, 1709, from yellow (adj.) + tail (n.).
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redstart (n.)

type of bird with a more or less red tail, 1560s, from red (adj.1) + start "tail," from Old English steort "tail, rump," from Proto-Germanic *stertaz (from PIE *sterd-, extended form of root *ster- (1) "stiff"). Similar formation in German Rotsterz; Dutch roodstaartje, etc.

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thresher (n.)

late 14c., agent noun from thresh. The thresher shark (c. 1600) so called for its long upper "tail," which resembles a threshing tool. The Greek for it was alōpēx, literally "fox," also for the tail.

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