You send your private sword man out with your shellfish so he can trade them. Shellfish were used as currency back in the olden days. And you aren't going to go out trading and dirty your own hands, no no. Trading your shellfish is the job for the private sword you hired!
While he's out making the trade for you, you decide to relax and do some bowling (ぼう). In fact, you can't wait for the trade to be done because you're hoping he's going to come back with a new bowling ball for you.