In the article Brief History of British Sign Language by signcommunity.org.uk, they talk about the poorly recorded early history of BSL.
“Early History of BSL
Since BSL is an unwritten language, its early history is poorly understood. The very few written records about the use of sign language by the deaf communities in Britain were almost exclusively created by the hearing people which makes them questionable in regard to the language itself. But there is solid evidence that deaf people in Britain were signing as early as in the 16th century although most scholars believe that they were signing earlier.”
So while there is a lot of myth and rumour about the history, the why and the what of BSL development there are still interesting little bits of story behind the signs. Keep an eye out for topic heading starting “Etymology of BSL” as dig up some of the background and perhaps the history of BSL signs.
Needless to say, if you know things about a sign we have missed then please leave a comment!