Etymology
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malt (n.)

"grain (usually barley) in which, by heat, the starch is converted to sugar," Old English malt (Anglian), mealt (West Saxon), from Proto-Germanic *maltam (source also of Old Norse malt, Old Saxon malt, Middle Dutch, Dutch mout, Old High German malz, German Malz "malt"), possibly from PIE root *mel- (1) "soft" via the notion of "softening" the grain by steeping it in water before brewing.

By the addition of hops, and the subsequent processes of cooling, fermentation, and clarification, the wort is converted into porter, ale, or beer. The alcoholic fermentation of the wort without the addition of hops and distillation yield crude whisky. [Century Dictionary]

Finnish mallas, Old Church Slavonic mlato are considered to be borrowed from Germanic. Meaning "liquor produced by malt" is from 1718. As an adjective, "pertaining to, containing, or made with malt," 1707; malt liquor (which is fermented, not brewed) is attested from 1690s. 

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whiskey (n.)

1715, from Gaelic uisge beatha "whisky," literally "water of life," from Old Irish uisce "water" (from PIE *ud-skio-, suffixed form of root *wed- (1) "water; wet") + bethu "life" (from PIE *gwi-wo-tut-, suffixed form of *gwi-wo-, from root *gwei- "to live").

According to Barnhart, the Gaelic is probably a loan-translation of Medieval Latin aqua vitae, which had been applied to intoxicating drinks since early 14c. (compare French eau de vie "brandy"). Other early spellings in English include usquebea (1706) and iskie bae (1580s). In Ireland and Scotland obtained from malt; in the U.S. commonly made from corn or rye. Spelling distinction between Scotch whisky and Irish and American whiskey is a 19c. innovation. Whisky sour is recorded from 1889.

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malt (v.)

mid-15c., malten, "to convert grain to malt," from malt (n.). Meaning "to make with malt" is from c. 1600. Related: Malted; malting. Malted (n.) "a drink with malted milk" is by 1945.

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scotch (n.1)

1778, elliptical for Scotch whisky. See Scotch (adj.).

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Scotch (adj.)

"of Scotland," 1590s, a contraction of Scottish. As a noun, by 1743 as "the people of Scotland collectively;" 1700 as "the sort of English spoken by the people of Scotland." 

Scots (mid-14c.) is the older adjective, which is from Scottis, the northern variant of Scottish. Scots was used in Scottish English until 18c., then Scotch became vernacular, but in mid-19c. there was a reaction against it because of insulting and pejorative formations made from it by the English (such as Scotch greys "lice;" Scotch attorney, a Jamaica term from 1864 for strangler vines).

Scotch-Irish is from 1744 (adj.); 1789 (n.); more properly Scots-Irish (1966). Commercial Scotch Tape (1945) was said to be so called because at first it had adhesive only on the edges (to make it easier to remove as a masking tape in car paint jobs), which was interpreted as a sign of cheapness on the part of the manufacturers. It had become a verb by 1955 and for a time was often printed without capitals.

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scotch (v.)

early 15c., scocchen "to cut, score, gash, make an incision," a word of obscure origin. Century Dictionary considers that it might be a deformation of scratch. Chronology rules out connection with scorch. Perhaps [Barnhart] from Anglo-French escocher, Old French cocher "to notch, nick," from coche "a notch, groove," perhaps from Latin coccum "berry of the scarlet oak," which appears notched, from Greek kokkos

The meaning "stamp out, crush" (often figurative, of abstract things) is by 1825, earlier "make harmless for a time, wound slightly" (1798), a sense that derives from an uncertain reading of "Macbeth" III.ii.13). Related: Scotched; scotching.

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scotch (n.2)

"incision, cut, score, gash," mid-15c., scoch, in cookery, related to scotch (v.). Compare Old French coche "notch on an arrow."

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Rob Roy (n.)

Highland freebooter and folk hero, Robert Roy MacGregor (1671-1734). His name means "Red Robert." Scott's novel first was published in 1817. As a type of cocktail made with Scotch whiskey, it is attested from 1960.

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malthouse (n.)

"building in which malt is made," late Old English mealthus; see malt (n.) + house (n.).

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maltster (n.)

"maker of or dealer in malt," early 14c. (late 13c. as a surname), from malt + -ster.

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