Oh my God is something someone may state when they are surprised about something or frustrated. An abbreviation that people may use to say “oh my God” is “omg” which means “oh my God,” or “oml”which means “oh my lord.”
An example:
Boy: *pees pants*
Other Boy: Oh My God/Lord, your a weirdo.
The /g/ sound is the the voiced cognate of the unvoiced /k/, and the /d/ sound is the voiced cognate of the unvoiced /t/, thus, articulator placement during production cat is identical to the production of the word god. God backwards may be dog, but God unvoiced is cat.