What is the origin of skerrick?

Skerrick, “a small piece or quantity; a bit,” used in the negative, as in “Not a skerrick of work got done,” is a slang term used nowadays mostly in Australia and New Zealand. Skerrick originated in Great Britain in the early 1820s as a slang term for halfpenny. As with most slang terms, the origin of skerrick is obscure: it may be a variant of scuddick, which also dates from the early 1820s, means the same thing as skerrick, and has an equally obscure etymology.