How do you plan on accessing the table data ?
If you're using something a bit flexible (your own code or simply SQl queries) then an easy way out is to copy the needed table to another database and the detach it from the server. Afterward, truncate the table (or delete the unwanted rows, although you might want to check your T-Log size of you do that).
When you'll need it, you can always remount the relevant database from storage in read only mode. If you need to run queries on multiple backups at once, you can create a view regrouping all the data.
If you're using a software that won't allow you to customize how that table is accessed, you can still copy the table to another database on its own but restoring that backup can be problematic because you'll need to merge the existing context (the other table states) with the old data. Plus, the data structure might have changed making it next to impossible to restore.
So in that case, I would suggest that you simply take a backup of the full database and store that (preferably along with a version of the software that accesses it).