Scotch mist is a thick drizzly mist of a kind common in the Scottish Highlands.
The term also has the general meaning of a steady drizzle. It was defined as “a sober, soaking Rain” in A New Dictionary of the Terms Ancient and Modern of the Canting Crew (1699), by “B.E. Gent.”.
A phrase is first attested in a 1589 tract entitled Pappe with an hatchet:
If you meane to gather clowdes in the Commonwealth, to threaten tempests, for your flakes of snowe weele pay you with stones of hayle; if with an Easterlie winde you bring Catterpillers into the Church, with a Northerne wind weele driue barrennes into your wits.
We care not for a Scottish mist, though it wet vs to the skin, you shal be sure your cockscombs shall not be mist, but pearst to the skuls. I professe rayling, and think it as good a cudgell for a Martin, as a stone for a dogge, or a whippe for an Ape, or poyson for a rat.
It had become a proverb in Paroemiologia Anglo-Latina in usum scholarum concinnata. Or proverbs English, and Latine, methodically disposed according to the common-place heads, in Erasmus his adages (1639), by the schoolmaster John Clarke († 1658):
A scotch mist, may wet an Englishman to th’ skin.
The Scottish climate was described in Letter from a Scotch physician to his friend in London, on the subject of a consumptive habit, &c., written in the mid-18th century:
Our mountains are so high, that a cloud can make no descent in our atmosphere, but it knocks against the proud tops of one or other of them, and covers the valley below with a deluge of rain, from which we are seldom twenty-four hours together free. The mountains are covered to the top with bogs and heath, which receive and detain every shower like a sponge, and retail them on the country in thick fogs, and Scotch mists, which, according to the old proverb, are sufficient to wet an Englishman to the skin.
Very early, Scotch mist was used figuratively to mean something that clouds a person’s perception or understanding, and something or someone considered as insubstantial or unreal. For example, in The Character of a London-diurnall with severall select poems (1647), the poet John Cleveland (1613-58) wrote:
This is he, that hath put out one of the Kingdoms eyes, by clouding our Mother-University, and (if the Scotch-mist further prevaile) will extinguish this other.
And the author and press censor Sir Roger L’Estrange (1616-1704) wrote in Considerations upon a Printed Sheet (1683):
This Paper is only a Scotch Mist from one End to the Other. There’s a bold Insinuation of Injustice; but not One Syllable in Proof, or so much as to Colour it.
In later use, Scotch mist has frequently been used sarcastically in rhetorical questions implying that the person addressed has failed to perceive something obvious. An example is found in the short story Out with the Girls (1962) by the English playwright, screenwriter, and author Nell Dunn (born in 1936):
‘Are yer married?’
‘Course she is. What do yer think that is? Scotch mist?’ Rube points to my wedding-ring.
Chiefly in the USA, a Scotch mist is a drink of whisky served with crushed ice and a twist of lemon. The American journalist and writer Westbrook Pegler (1894-1969) mentioned it in a text published in several newspapers on 12th November 1947:
Two bourbon-soda and for me a Scotch mist;
And now leave us take a gander at the list.
Wonderful steaks here, Idaho potato, corn beef, pot roast.
There’s Ed! Hi, Eddie boy! How’s things on the coast?