Etymology
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seal (n.1)
"design stamped on wax," especially one attached to a document as evidence of authenticity, c. 1200, from Old French seel "seal on a letter" (Modern French sceau), from Vulgar Latin *sigellum (source of Italian suggello, Spanish sello; also Old Frisian and Middle High German sigel, German Siegel), from Latin sigillum "small picture, engraved figure, seal," diminutive of signum "identifying mark, sign" (see sign (n.)). An earlier borrowing directly from Latin is represented by Old English insigel. Technical use, "what prevents the escape of a gas or liquid" is from 1853.
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seal (n.2)
fish-eating mammal with flippers, Old English seolh "seal," from Proto-Germanic *selkhaz (compare Old Norse selr, Swedish sjöl, Danish sæl, Middle Low German sel, Middle Dutch seel, Old High German selah), of unknown origin, perhaps a borrowing from Finnic. Seal point "dark brown marking on a Siamese cat" is recorded from 1934, from the dark brown color of seal fur; compare seal brown "rich, dark brown color," by 1875. Old English seolhbæð, literally "seal's bath," was an Anglo-Saxon kenning for "the sea."
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seal (v.)
"to fasten with (or as with) a seal," c. 1200, from seal (n.1). Meaning "to place a seal on (a document)" is recorded from mid-14c.; hence "to conclude, ratify, render official" (late 15c.). Sense of "to close up with wax, lead, cement, etc." is attested from 1660s, from the notion of wax seals on envelopes. In reference to the actions of wood-coatings, 1940. Related: Sealed; sealing. Sealing-wax is attested from c. 1300. To seal (one's) fate (1799) probably reflects the notion of a seal on an execution warrant.
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sealskin (n.)
early 14c., from seal (n.2) + skin (n.).
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unseal (v.)
early 15c., from un- (2) "reverse, opposite of" + seal (v.). Similar formation in Middle Dutch ontsegelen, Old High German intsigilan. Related: Unsealed (late 14c.).
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signet (n.)
late 14c., "small seal" (especially one on a finger ring), from Old French signet "a small seal," diminutive of signe "sign" (see sign (n.)).
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cachet (n.)
1630s, "a seal," Scottish borrowing of French cachet "seal affixed to a letter or document" (16c.), from Old French dialectal cacher "to press, crowd," from Latin coactare "constrain" (see cache). Meaning evolved 18c. (via French lettre de cachet "letter under seal of the king") to "(letter under) personal stamp (of the king)," thence to "symbol of prestige" (1840).
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Orkney 

group of islands off the north coast of Scotland, from Old Norse Orkney-jar "Seal Islands," from orkn "seal," which is probably imitative of its bark. With Old Norse ey "island" (compare Jersey). Related: Orcadian; Orkneyman.

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floe (n.)

1817, first used by Arctic explorers, probably from Norwegian flo "layer, slab," from Old Norse flo, from Proto-Germanic *floho-, from PIE root *plak- (1) "to be flat." Related to first element in flagstone. Earlier explorers used flake. Floe-rat was a seal-hunter's name for the ringed seal (1862).

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