Wordorigins.org

These two interjections have both been popularized by cartoons.

The first, doh, has been made famous by Homer Simpson, but he was not the first to use it. That honor goes to the BBC radio show It’s That Man Again. From a 1945 script from that show:

Diana: The man I marry must be affectionate and call me “Dear"—
Tom: Oh you’re going to be a stag’s wife—
Diana: Doh!
Tom: Same thing.