In Ruth 3:3ff, Naomi tells Ruth to "wash and anoint yourself, and put on your best clothes...when [Boaz] lies down, observe the place where he lies; then, go and uncover his feet and lie down; and he will tell you what to do." The New Oxford Annotated Bible suggests that in Hebrew, feet are a euphemism for genitals. Ruth asks Boaz once he wakes up and notices her there to spread his cloak over her, which might imply she asking him to marry her, increasing the sexual undertones in the passage. Boaz does eventually marry Ruth and she bears him a son. The literal translation "he went into her" is rendered as "when they came together" in their conjugal union. Their baby becomes the grandfather of David, making Ruth the great^n -grandmother of Jesus.

So there's some evidence from the Hebrew Bible.

The name of Oedipus, the mythical Greek king, could be literally translated to English by "swollen foot". I am not sure whether you were hoping for this kind of etymological references, but knowing that it was Freud who coined the "Oedipus complex" (sexual attraction of a child to his/her parent of the opposite sex), the link between this mythological figure and primitive sexual symbols might be interesting.

Remarkably, this topic has come up before. I won't say the thread explored the subject thoroughly, though.