From Wikimon

Why was this moved back to Erismon from Herissmon? Here’s the source for Herissmon: pic, album, Reddit thread, comment on WtW. An art book may not be the best source, but as far as I’m aware, there are no remotely officially sources spelling it “Erismon” at all. (Am I wrong?) The etymology listed on the page says it’s from the French hérisson, which also matches “Herissmon” nicely. What’s the rule here? Do we have to wait until the name shows up in a reference book? Even if we assume the art book is not a credible source and there is no official spelling known yet, why is “Erismon” being preferred in the interim? Chortos-2 (talk) 13:28, 5 February 2019 (CST)

In case anyone thinks Herissmon is pronounced differently from Erismon and hence doesn’t match the kana: nope, the pronunciation is the same, because French <h> is silent. Chortos-2 (talk) 15:50, 5 February 2019 (CST)
The official romanization from the Digimon Pendulum Artbook is fine enough as for now. Furthermore, it normally matches the ones in the DRB. I lean more towards Erismon, but it's more a personal preferencr though. --Shadow Shinji (talk) 19:02, 5 February 2019 (CST)