We have notes for figures of speech, but the point of this note is that it is not a euphemism. I don't think it is needed. So I deleted it. ("Feet" only occurs twice in Sng. The next is Sng 7:1, and there's no reason to see that as a euphemism.)
I have washed my feet
While the word "feet" can be a euphemism for private parts, this probably refers to literal feet. The woman seems more likely to want to make love than to want to refrain from lovemaking because she has just bathed. (See: rc://en/ta/man/translate/figs-euphemism)