1832, Edward Bulwer Lytton, Eugene Aram
Lester's good heart will be to hear that little Peter is so improved;--no longer a dissolute, harum-scarum fellow, throwing away his money, and always in debt.
adverb
wildly, carelessly, irresponsibly
1800, Maria Edgeworth, Castle Rackrent
[…] for he never looked after anything at all, but harum-scarum called for everything as if we were conjurors, or he in a public-house.