Dear Rouspeteur: Very interesting. Was there any etymology given for the new word "la herse"?
I looked up "hearse" and was surprised to find this:

"hearse"
n.
ME herce < OFr, a harrow, grated portcullis < L hirpex, a large rake with iron teeth < dial (Sabine) irpus, wolf (hence, lit., wolf-tooth device)

It sounds as though the two words had co-existed in French, and then portcullis became obsolete.