smashing

Origin

From smash + -ing. As a synonym for wonderful, the term first appeared in the United States in the early twentieth century, and possibly derives from the sense of smash used in smash hit and similar terms. Popular folk etymology connects the term to the broadly homophonous Irish is maith sin or Scottish Gaelic 's math sin ("that is good"), but this has been described as "improbable", and does not appear in the etymological dictionaries.