I’ve often wondered about the origin of this expression, which is Rightpondian slang for “malingering”, usually by feigning illness, especially in the armed services. A Google search tells me that a lot of other people have wondered about it too (over 2 million hits on “swinging the lead”, many questions), not to much effect. Lots of folk etymology (much of it from people with no idea at all of what is involved in taking soundings at sea with a lead; they seem to think it was a cushy job). Even mr. Quinion admits to not having much to offer concerning the etymology of this term, though his examination of the subject does away with a lot of the rubbish. Perhaps someone here has something substantial to offer --- if not of etymology, then perhaps of earliest recorded use?
(I apologize if this has already been discussed before my time)