Biwabokuboku is a Japanese specter that is introduced in "Hyakki Tsurezure Bukuro" (One hundred bags in idleness), a collection of specters illustrations by Sekien TORIYAMA, and it is a specter of biwa (Japanese lute).
琵琶牧々（びわぼくぼく）は、鳥山石燕による妖怪画集『百器徒然袋』にある日本の妖怪の一つで、琵琶の妖怪。