I think many people confuse billys (goat bucks) and rams, maybe because they cannot imagine a sheep being aggressive and headbutting like a ram does, since it is more associated with goats (ironic since it's also literally called ramming).

I have also seen people mistake sheep with prominent horns for goats, even though all other features are very sheep like. I guess it is just that when people hear sheep, they think of a female 'ovis aries'; and when they hear goat, they think of a male ibex or a rocky mountain goat. The latter of which coincendentally not even being a true goat scientifically speaking, but rather a goat-antelope (a near cousin evolutionary wise).