In yesterday's ten letter game SHONKY was rare and YONKS was common. Both were classed as Australian, NZ, English slang.
I have to say that if you make one rare or common, they both should probably rate the same although I never tried YONKS.
Yes I've heard of it but I thought of SHONKY first and didn't even think of trying YONKS, on the strength that Shonky was rare.