WHY DID I NOT PUT IT TOGETHER BEFORE!
Of COURSE "Sebun" is "Seven"...
I kind of assumed that everyone one of the "Livestock" from Louis' time there would have been sold off and eaten already (it was like 14-ish years ago) and I certainly didn't think they'd just go around calling each other by their numbers! But it makes absolute sense now.
and I wonder if Paru is planning on doing anything with the fact that "San" and "Kyuu" together is "Sankyuu" the Japanese pronunciation of "Thank you".
"39" has been Japanese texting shorthand for that beginning in the 1990's.