From The Collaborative International Dictionary of English v.0.48:
Doublet \Doub"let\, n. [In sense 3, OF. doublet; in sense 4, F.
doublet, dim. of double double. See Double, a.]
1. Two of the same kind; a pair; a couple.
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2. (Print.) A word or words unintentionally doubled or set up
a second time.
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3. A close-fitting garment for men, covering the body from
the neck to the waist or a little below. It was worn in
Western Europe from the 15th to the 17th century.
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4. (Lapidary Work) A counterfeit gem, composed of two pieces
of crystal, with a layer of color between them, and thus
giving the appearance of a naturally colored gem. Also, a
piece of paste or glass covered by a veneer of real stone.
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5. (Opt.) An arrangement of two lenses for a microscope,
designed to correct spherical aberration and chromatic
dispersion, thus rendering the image of an object more
clear and distinct. --W. H. Wollaston.
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6. pl. (See No. 1.) Two dice, each of which, when thrown, has
the same number of spots on the face lying uppermost; as,
to throw doublets.
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7. pl. [Cf. Pr. doblier, dobler draughtboard.] A game
somewhat like backgammon. --Halliwell.
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8. One of two or more words in the same language derived by
different courses from the same original from; as, crypt
and grot are doublets; also, guard and ward; yard and
garden; abridge and abbreviate, etc.
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