I was baffled by the "We came up with the name based on some Japanese wordplay" as it didn't seem like an actual explanation and no TL note was around, so I checked the raw. It's literally unexplainable.
Raw was 「おさ"なな"じみが4人だから"なななな"」 (osa"nana"jimigayonindakara"nananana")
In English, it's...