I am not a teacher.<snip>
Also it means "For Christ's sake".
I am not a teacher.
Right. It is a euphemism for that. The first part of "for crying out loud"---"for cr..."---is the same as the first part of "for christ's sake". The speaker is supposed to have started to blaspheme and changed his mind, smoothly going over to a bland utterance.
I am not a teacher.Thanks to all.
But I still don't get it as Ksyuk said it's to emphasize what we are saying informal while Coolfootluke said it's euphemism.
Is it the same as My god, Oh gosh, Jesus?
Thanks.
I am not a teacher.
Ksyuk got it a little bit wrong, I think. "For crying out loud" expresses, as Barb_D said, annoyance or exasperation. So does "For Christ's sake", but we use the euphemism to avoid offending God.