I just know because I know, that Bert's right: it's about sex, and 1amarca with Richard Thompson's song shows where the subconscious goes when whipped out, because that's what it's all about, in and out, it doesn't matter whether it's a hand or a leg, and the person that originally "wrote" the song may say he was only thinkin' of legs and arms, but why think or say that, when that's not really what it's all about?