There's a character in 13 Sentinels who Joe referred to as "oomfie boomfie".[1] This is because there's a genre of gifs that get posted a lot on JADS which depict Klee from Genshin Impact accompanied by text containing the word "oomfie", and Joe probably thought the 13 Sentinels character looked like Klee.

References

  1.     “Falco” video: “Joseph Anderson 13 Sentinels stream 5 with chat [04/04/2023” at 01:49:17].