Wasnt it because some guy missed an Indian condiment
I hadn't heard this part, but yes the company claims something like this. Apparently Lord Sandys commissioned a local pharmacist to recreate some sauce he had encountered while in India
Funnily enough though, Lord Sandys had never been a governor of Bengal (as they claim) nor is there a record of him ever visiting India

likely they just made up lore to make it seem more fancy and "oriental"
Apparently the first attempt at making the sauce was so strong it was inedible, so they left it in the basement. The pharmacist tried it again 18 months later and apparently the aging had mellowed it out. Personally, I believe this aging to mellow it out is the only part of the story that is true (having made garum myself, I can also note that you do NOT want to keep it in a basement or anywhere nearby civilization)