Etymology
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dormer (n.)

also dormer-window, "window standing vertically in a projection built out to receive it from a sloping roof," 1590s, from French dormeor "sleeping room," from dormir "to sleep," from Latin dormire (see dormant). So called because they were chiefly in upper bedrooms.

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casement (n.)
type of hinged sash-window that swings open like doors, early 15c., originally "hollow molding, frame for glass," probably a shortening of Old French dialectal enchassement "window frame" (Modern French enchâssement), from en- "in," prefix forming verbs, + casse "case, frame" (see case (n.2)) + -ment. Or possibly from Anglo-Latin cassementum, from casse. The "window" sense is from 1550s in English. Old folk etymology tended to make it gazement.

The Irish surname is originally Mc Casmonde (attested from 1429), from a misdivision of Mac Asmundr, from Irish mac "son of" + Old Norse Asmundr "god protector."
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fenestral (adj.)
late 14c., "pertaining to windows," from Old French fenestral, from fenestre "window," from Latin fenestra (see fenestration).
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transom (n.)

late 14c., transeyn "crossbeam spanning an opening, lintel," probably by dissimilation from Latin transtrum "crossbeam" (especially one spanning an opening), from trans "across, beyond" (from PIE root *tere- (2) "cross over, pass through, overcome") + instrumental suffix -trum. Meaning "small window over a door or other window" is first recorded 1844.

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vitrine (n.)
"glass show-case," 1880, from French vitrine, from vitre "glass, window-glass," from Latin vitrum "glass" (see vitreous).
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sash (n.2)

framed part of a window, into which the panes are fitted, 1680s, sashes, a mangled Englishing of French châssis "frame" of a window or door (see chassis).

The word was mistaken as a plural and further mangled by loss of the -s by 1704. Sash-door, one having panes of glass to admit light, is by 1726; sash-weight, attached by cords to either side of a sash to balance it and make it easier to raise and lower, is attested by 1737.

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staircase (n.)
also stair-case, 1620s, originally the enclosure of the stairs, from stair + case (n.2) in its sense "frame;" compare former window-case, door-case.
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defogger (n.)

"mechanism that clears condensed water vapor from the window of an automobile," by 1962, from agent noun from defog (v.) which is attested from 1945 (implied in defogging); see de- + fog.

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jamb (n.)
side-piece of an opening of a door, window, etc., early 14c., from Old French jambe "pier, side post of a door," originally "a leg, shank" (12c.), from Late Latin gamba "leg, (horse's) hock" (see gambol).
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fenestration (n.)

1870 in the anatomical sense, noun of action from Latin fenestrare, from fenestra "window, opening for light," a word perhaps from Etruscan (see defenestration). Meaning "arrangement of windows" as a design element in architecture is from 1846. Related: Fenestrated.

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