Super bummed I'm not getting the joke. What's the segue to 8th month (August) and October (10th month) from

    calvin@bison:~/work$ tree -d | head
    .
    ├── 2022
    │   ├── 04
    │   │   ├── 19

?

octo is latin for 8.

just like septem is 7, novem is 9 and decem is 10.

so the parent comment is saying that while at one point it may have been possible to derive the name from the number of the month, that is no longer the case because names and numbers do not match up and therefor the name would not be undevigintiber. thought it might be septendecimber ;-)