How do I purge wp_termmeta (250K+ rows)?

I’ve been working on the site for a year. Later and later the backup and restore became longer and longer. The file sizes became larger as well. I had to extend backup and restore timeouts longer and longer.

The issue is with the wp_termmeta table. It has 250K+ records in it.

How can I purge it? I need to know which records can be kept or deleted.

The site uses 30 WooCommerce custom attributes. The names and values have changed over the year. Products have repeatedly imported (some 1,000 records an import, totaling maybe 12,000 records over the year).

Many Thanks, Caesar.