Meaning of “Outen(横転)”

As a slang, “Outen(横転)” means to be surprised that you metaphorically fall over – like a comic reaction of shock.
The original meaning of this is falling over sideways physically.
Lately, I’ve been seeing this slang a lot on social media.

Example Conversation on social media

A: I totally thought she was a super rich, but I saw her profile. Outen(横転).
B: Yeah, PapaKatsu(パパ活) girl.

A: てっきりガチの金持ちかと思ったのに、プロフ見て横転
B: パパ活勢だな