1
general::
An exclamation of anger or exasperation, as in For crying out loud, can't you do anything right? This term is a euphemism for "for Christ's sake." [Colloquial; early 1900s]
American Heritage Idioms
2
general::
Phrase(s): For crying out loud! [and] For crying in a bucket!
Inf. an exclamation of shock, anger, or surprise. • Fred: For crying out loud! Answer the telephone! Bob: But it’s always for you! • John: Good grief! What am I going to do? This is the end! Sue: For crying in a bucket! What’s wrong?
McGrawhill's American Idioms And Phrasal Verbs