LOL, I had no clue until the Internet came along what he was singing.
Yeah the days before lyrics on demand were interesting. I like listening to Otis Redding records and catching when he got the lyrics wrong on a song he was covering. Happened quite a lot.
Turns out the Stax guys would just go to the record store downstairs and listen to a 45 of whatever they wanted to cover and try to write down whatever lyrics they could make out. If they couldn’t figure it out, then he’d just make something up that sounded good.