It has been said that ‘(as) right as a trivet’ an alteration of ‘(as) tight as a rivet’. But the latter phrase, which postdates the former, originally meant ‘extremely tight’, not ‘thoroughly or perfectly right’.
USA, 1890—a participle, often found at the beginning of a sentence, that appears from its position to modify an element of the sentence other than the one it was intended to modify
proprietary name for a soft drink supposed to maintain or restore the body’s alkaline balance—Ireland & UK, 1986—from the Latin nouns ‘aqua’ (water) and ‘libra’ (a balance)
a moment of sudden discovery, inspiration or insight—1918—from the reputed exclamation of Archimedes when he realised that the volume of a solid could be calculated by measuring the water displaced when it was immersed
a humorous redefinition of an existing word or phrase, presented as a dictionary definition—USA, 1910—a blend of the adjective ‘daffy’ and of the noun ‘definition’
USA, 1871: a person who frequently uses or coins slang words and phrases—USA, 1926: a person who studies the use and historical development of slang—blend of the nouns ‘slang’ and ‘linguist’
UK, 1856—a talisman associated with a woman—a woman likened to a talisman, especially a female sports player regarded as the leading representative of her team—alteration of ‘talisman’ with substitution of ‘woman’ for the element ‘‑man’
to make bigger or greater, to enlarge—UK, 1884, as a translation of ancient Greek ‘μεγαλύνειν’ as used in the Acts of the Apostles, 5:13—recoined in 1996 in the U.S. animated television series The Simpsons