Etymology
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laser (n.)
1960, acronym for "light amplification by stimulated emission of radiation," on pattern of maser (1955). A corresponding verb, lase, was coined by 1962. Related: Lasered; lasering. Laser disc recorded from 1980. Earlier laser was the name of a type of gum-resin from North Africa used medicinally (1570s), from Latin; still earlier it was an Old English and Middle English name for some weed, probably cockle.
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beam (n.)

Old English beam originally "living tree," but by late 10c. also "rafter, post, ship's timber," from Proto-Germanic *baumaz "tree" (source also of Old Frisian bam "tree, gallows, beam," Middle Dutch boom, Old High German boum, German Baum "tree," and perhaps also (with unexplained sound changes) Old Norse baðmr, Gothic bagms), which is of uncertain etymology (according to Boutkan probably a substrate word). The shift from *-au- to -ea- is regular in Old English.

Meaning "ray of light" developed in Old English, probably because beam was used by Bede to render Latin columna (lucis), the Biblical "pillar of fire." Meaning "directed flow of radiation" is from 1906. To be on the beam "going in the right direction" (1941) originally was an aviator's term for "to follow the course indicated by a radio beam." Nautical sense of "one of the horizontal transverse timbers holding a ship together" is from early 13c., hence "greatest breadth of a ship," and slang broad in the beam, by 1894 of ships, of persons, "wide-hipped," by 1938.

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beam (v.)
"emit rays of light," c. 1400, from beam (n.) in the "ray of light" sense. Sense of "shine radiantly" is from 1630s; that of "smile radiantly" is from 1804; that of "to direct radio transmissions" is from 1927. Related: Beamed; beaming.
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balance-beam (n.)
1798 as the cross-piece of a scales, 1813 as a type of device on a drawbridge, canal-lock, etc., from balance (n.) + beam (n.). From 1893 as a type of gymnastics apparatus.
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cross-beam (n.)

"large beam going from wall to wall; girder which holds the sides of a building or ship together," c. 1400, from cross- + beam (n.).

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I-beam (n.)
1869; see beam (n.). So called for its shape. I-bar is from 1890; also I-rail (1873).
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maser (n.)

a type of laser that emits microwaves, 1955, acronym from "microwave amplification (by) stimulated emission (of) radiation." Related: Mase (v.).

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abeam (adv.)
"at right angles to the keel" of a ship, hence in line with its beam, 1826, nautical, literally "on beam;" see a- (1) + beam (n.) in the nautical sense.
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summer (n.2)
"horizontal bearing beam," late 13c., from Anglo-French sumer, Old French somier "main beam," originally "pack horse," from Vulgar Latin *saumarius, from Late Latin sagmarius "pack horse," from sagma "packsaddle" (see sumpter).
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architrave (n.)
1560s as a feature of architectural columns; 1660s of window parts, from Italian architrave, from Latin archi- "beginning, origin" (see archon) + Italian trave "beam," from Latin trabem (nominative trabs) "beam, timber," from PIE root *treb- "dwelling" (see tavern).
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