See 膠 as the original glyph. It is difficult to associate elements of「exchanging meat, mixing meat」with a SHINBONE, unless one realizes that these elements also combine to mean ANYTHING STICKY, and the tibia is a likely place where spunk would land if all participants were sitting cross-legged in a circle. It would also make sense if one is aware of the dynastic Chinese practice of foot-dis-integrating/binding and the use of mashed feet during「sexual relations with meat」with the SHINBONE as a sound handle.
SOUND refers to「transmitted vibrations」so,…is that the sticky noises emanating, or, good thinking? something SOUND is also「having a firm basis, unshakable, thorough, complete, deep and unbroken」
[ https://www.thefreedictionary.com/sound…but note that not all the English definitions apply equally in this case ]
Euphemistically, the INTERSECTION OF MOON AND SUN refers to ying-yang, female-male activity, respectively, likely related to joint exercises of 肞 with 交, co-educational autoeroticism sessions and the female self-pleasuring as the male intersects with her no-longer-integrated foot, and the goo flies. In fact, when the Sun and Moon intersect as viewed from the surface of the Earth, a solar eclipse occurs and the Moon's shadow passes across planet Earth, or, a lunar eclipse occurs and the Earth's shadow passes across the surface of the Moon…a 'soiled' moon-ying because the sun-yang covered it, but only one small circular dark spot. This same phenomenon can certainly apply to a no-longer-integrated foot and what may be eclipsed as viewed from the perspective of the masturbating client. Nonetheless, the STICKY, GOOEY, soundly attached yang (Sun) passing over the ying (Moon) to cause a full shadow 'eclipse' (means 'failing to appear for a while') suggests foregoing the no-longer-integrated foot altogether, and diving down into the groin: perhaps the source of the English expression,「take a flying fuck at a rolling doughnut, take a flying fuck at the moon」(the rolled doughnut was the shape of her no-longer-integrated foot prior to the flying dive into the groin. And who would seriously attempt to have intercourse with the Moon?).
Without a doubt, the Irish also have knowledge of their own to pass along in these trying times:「Masturbation will not spread coronavirus, especially if you wash your hands (and any sex toys) with soap and water for at least 20 seconds before and after.」Nonetheless and regrettably, unlike in dynastic China, it must be undertaken alone to truly be a preventative countermeasure but still achieve the desired result with some degree of safety.
[ https://www.sexualwellbeing.ie/sexual-health/sex-and-coronavirus/ 2020-03-31 ]
The Dutch, too have the same solution—it seems masturbation has become mainstream in the media the world over due to the coronavirus (it has always been 'the main stream' in reality, albeit covertly for most folks):
「'Don't have sex with your partner if they have been isolated because of (suspected) coronavirus infection,' the RVIM says. 'Sex with yourself or with others at a distance is possible (think of telling erotic stories, masturbating together).'」
[ https://www.theguardian.com/world/2020/may/15/dutch-official-advice-to-single-people-find-a-sex-buddy-for-lockdown-coronavirus 2020-05-16 ]
Needless to point out perhaps, but Chinese shamans from antiquity hit upon the same solution as a pandemic preventative countermeasure, honed for ultimate client satisfaction by utilizing naked females with no-longer-integrated feet as masturbatory sex buddies available for short-term rental with erotic visualization of live prepubescent female genitalia engaging in autoerotic stimulation herself, as a solution to the same problem facing us now, but in pre-Internet days.

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Unihan extended: the shinbone, or tibia, (same as 交) to intersect, the sun and the moon in the sky, (simpfied form 膠) glue; gum, resin; sap, anything sticky