being more common in downmarket British tabloid newspapers such as the Sun and the Mirror. It seems to have been first recorded in the 1960s:
Eli: Go round talking like that, you’ll be hearing from our solicitor.
Nellie: He is our solicitor, you big girl’s blouse.
Nearest and Dearest, Series 2, Episode 1, 1969. This ITV network sitcom starred Jimmy Jewel as Eli Pledge and Hylda Baker as his spinster sister Nellie, who inherit a pickle-bottling factory in Colne, Lancashire. It was rough-and-ready Northern humour, full of innuendo (plus malapropisms from Nellie). This is the earliest example so far known.
It has been suggested that Hylda Baker invented the phrase in her stage act. If she didn’t, where big girl’s blouse came from is likely to remain a mystery. However, as a possible clue, Brian Edmondson told me that his Liverpudlian father, who died in 1979, always said “he’s flapping like a big girl’s blouse”. This conjures up the twin ideas of a large garment flapping on a washing line and of a man flapping in the sense of panicking. It’s plausible as the image from which the current version could have evolved.