This is a post, where if it gets any Google traffic over time, you know it's going to be from some weird-ass people. (I'm posting it, so I guess I fall into that group).
I was listening to my Deadbolt Hobo Babylon CD yesterday, and every time I listen to it I get frustrated because the CD has the f-words beeped out. There are a lot of f-words on that album, and the beeps get quite distracting. That got me sensitive to 'explicit lyrics', and then later in the day I was listening to something else, and realised that the song I was listening to was pretty old, but had the f-word. When did people first start cussing in modern music, I wondered?
Wikipedia awards the honours for the first use of the word 'fuck' in a (rock) song to The Doors ('The End' from 1967). Other uses of the word are credited to The Beatles (a line in 'Revolution 9', from 1968, although I'm not sure if anything from Revolution 9 really counts as 'lyrics'), and John Lennon's 'Working Class Hero' from 1970.
The song I was listening to was 'Tired', by German group Dies Irae, from their one and only album, First, from 1971. It wasn't the first song to use the word 'fuck', but it must be one the first songs to use the word 'motherfucker'. (Update: meh, posted too soon. Went back and re-listened on earphones and it might be 'mindfuckers'. Which would be even more obscure. Crazy German accents.)
So anyway. As I stumble across more really old songs with cuss-words, I'll add them to this post. If you know of any to add, please feel free.