Re: Middle Rhenish Lamentation
This from Ben Armhardt's The Testimony of Nathan Son of Isaac Concerning Jesus of Nazareth: "Although Steinberg calls no attention to it, the peculiar posture of a female mourner in an anonymous Middle Rhenish Lamentation c. 1450 (p. 170, Fig. 188) is suggestive of fellation; this may hint at that particular artist's familiarity with an unfiltered version of the Testimony." (pp. 27-28)
The blasphemous subject has also been taken up by contemporary artists; see, for example, Michael Thompson's Christo Paternoster Recusant.