USA 1920: ‘to have the brains of a goldfish’ (to have limited intelligence)—USA, 1958: ‘to have the memory of a goldfish’ (to be unable to retain information or memories for any significant length of time)
American English, 1874—used in particular of stupidity, as in ‘dumb as a bag of hammers’ and variants—the underlying notion is probably that anything is dumb that does all the hard work
Britain, 1747: dew of the kind that settles on mountains—Scotland, 1816: whisky or other spirit, especially when home-made or illicit (originally in reference to whisky distilled in the Highlands, i.e., in the mountainous region of Scotland)
USA, 1977—petroleum, and any liquid derived from petroleum used in a vehicle powered by an internal-combustion engine—perhaps from popular association of ‘dinosaur’ with ‘fossil fuel’
UK, 1759: first applied to Japan—1794 (during the French Revolution): the disparaging use in reference to Britain was popularised by the French phrase ‘nation boutiquière’
USA, early 1930s—adjectives—‘little-girl-lost’: resembling (that of) a small girl who has lost her way—‘little-boy-lost’: resembling (that of) a small boy who has lost his way
UK, 1839—jocular variant of ‘penny-a-liner’ (i.e., a journalist who was paid at the rate of a penny a line, a person who produced mediocre journalistic work) with the implication that such journalists fabricated falsehoods