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[Need Origin, Spread, Internet Context, Popularity, etc.- if possible]

About

OMG is an initialism for the popular phrase, "Oh My God" (or occasionally, "Oh My Goodness" or "Oh my Gosh"). It is typically used to express disbelief.

The initialism is very popular on online chats, forums, and image macros. One image macro example would be its usage in LOLcat images. However, it has also been used in real life conversations as well, where OMG is pronounced as one word.

Derivatives

Variations on the OMG include "OMFG" (Oh My F*cking God), ZOMG (OMG with a "Z" thrown in it for the lulz, possibly originating from a typo, and often backronymed to "Zebras, Oh My God"), OMGOSH/OMGSH (Oh My Gosh), along with many others.

OMG is often combined with WTF (What the F*ck), like in: "OMGWTF" (Oh My God What The F*ck) and OMGWTFBBQ (Oh My God What The F*ck Barbecue).

It is also an important component to a few memes, including: OMG Cat, OMG Secret Nazi, and the previously mentioned OMGWTFBBQ.

OMG compared to other internet slang.