"reasonably familiar". In this series we're culling words that don't often see the light of day, though I admit we had a hard think about whether or not those two words made the cut.
I'm OK with couth not being here, but forth is pretty common. It's a 71 frequency in the Kucera-Francis corpus- a lot higher than other answers: e.g., firth doesn't appear, broth is 3, width is 17.