Prune unused taxonomy terms

Hi folks,

I’m looking for a way to command my database to dump all taxonomy terms that aren’t associated with any posts.

My scenario is this: An antiques dealer wants to associate a product number prospective buyers can quote to him and then look up himself. I’ve done this by adding a taxonomy to the post type handling his product entries. When he’s done he’ll delete the product’s post. To avoid cluttering the drop-down he’ll have to reference it needs pruning maybe once a month.

Could a simple php file do this regularly? I have 0 PHP knowledge, fyi.

I’m also open to novel suggestions in regards to product numbering as he’s an older man and needs things to be as non-technical as possible.

Thanks!