This is a variation of the usual ask the other guy to say "pizza" 10 times, then point to one's elbow (hiji) and trick the other person into saying "hiza" (knee) instead of "hiji".

Here Tamamo is expecting Oguri to say "Hiji Amazon", but Oguri being Oguri went for "Hijiki" instead (a type of seaweed that can look like messy black/brown hair), pissing off Hishiama (basically calling her "seaweed head").