I'm writing a short story set during WWI, in which the characters are English soldiers. I need a slang term for condoms which was current at that time, and I'm having difficulty finding one; I've Googled for "johnny" and "rubber johnny", but it looks as though that's a later term, and "slang condom" doesn't give me anything useful. Can anyone point me in the right direction?
Edited to add; Many thanks for all your responses; "French letter" sounds slightly more formal than I want, so I shall use "Frenchie" instead. And now I have some interesting resources to play with next time I need some slang; much appreciated!