бить баклуши

Etymology
, which is now only used idiomatically, originally meant a stick or plank of split wood that is used for making wooden dishes, spoons, toys, etc.

Vladimir Dal' claimed that chopping a short wooden block (bolt) in smaller pieces is allegedly an easy task, but modern scholars reject his etymology (even though it's still widespread).

According to Mokiyenko, dialectal and foreign Slavic material rather indicates that it was a metaphor for playing gorodki.

Alternatively, Moldavan suggested that the idiom may originally have meant playing music with wooden spoons and similar makeshift percussion instruments.

Verb

 * 1)  to loiter, to twiddle one's thumbs