I’m looking through the article’s edit history, and “Pipis Route” was because an editor created the Ch 2 Weird Route article on September 18, which was a day after the Chapter 1&2 demo released on September 17, 2021.
On September 19, there was some discussion about renaming the article.
Gil actually had moved and renamed the article to “Weird Route” on September 19 too, as he pointed out that it is listed as such in the game files. Based on Gil’s past summary replies, apparently there were people suggesting a lot of alternate names, primarily “Snowgrave,” and some edit warring occurred, and Jacky720 locked it.
A community vote occurred on the Fandom site roughly some days after, with “Snowgrave” being favored. Kocka had moved it to “Snowgrave Route” on October 9, 2021 per community voting.
There was some partial mentions of “Genocide Route” in the article’s history summaries, but like Cerulean mentioned, Snowgrave Route was favored, and all these alternate names happened on early release.
Unfortunately, it seems like some sites like “Archive of Our Own” has “Pipis Route” as part of its tag because of its early article name, and fans wanting to write stories based on Weird Route.