Linguistic anachronism in Downton Abbey

For a series that pays such exquisite attention to period detail in manners, clothing, and design, down to the very degrees of colour gradation in phases of mourning, Downton Abbey plays surprisingly fast and loose with the language. This is all the more surprising because doing research to find out whether a word existed at the time in question is much easier than researching fashion and interior decor: all you have to do is consult the Oxford English Dictionary online, which is available through most public libraries.
 Last night, Mr. Bates called Jimmy a "big girl's blouse", a British English term for a feeble or cowardly man. The OED's earliest quotation for this is from 1969. Hearing it used in the 1920s was as jarring for me as if Lady Mary had suddenly turned up dressed like this:



For another Downton-inspired post, on the word "valet", please click here.
For more linguistic anachronisms in Downton, see this post.