What is the origin of the term old bag as a derogatory term for an older lady?
In the UK it is exclusively used to describe females. There appears to be nothing intrinsically feminine about bags. Could it be a corruption of old hag?
Not so much a corruption of old hag as rhyming slang for it. The New Partridge Dictionary of Slang and Unconventional English quotes Ray Puxley, an expert on Cockney rhyming slang, as suggesting this might be the case.
old bag noun
The Online Etymology Dictionary says it dates from 1924 or earlier but does not give any sources.