「Flow, old, meat」may have at first been referring to the stagnant pooling of juices that forms underneath a large piece of rancid meat left forgotten in a pantry as maggots devour it.
All elements taken individually as「fluid flows from screwing orifice with meat」「buying and selling, bill for services with meat」「trading meat」describes the floor of a cave o' wonders, suggesting a POOLING OF FLUIDS (admittedly an inductive leap in logic here, nonetheless).「Fluid flows with hairy meat」confirms a pooling of liquids forming under a well-used service provider, or a very ill patient, or someone with a large beard…lakes formed geologically do not often contain much actual hair, but may be surrounded by marsh reeds and grasses that resemble hairs, in a way.
Left and center elements together mean「flow from old, inferior quality」as turbid, thickened and coagulated, not flowing cleanly like a river any longer, clotted fluids pent up in the enlarged prostate gland of an old man. Center and right elements together mean「old meat, blunder, reckless, foolish」such as catching the clap, or, eating「old meat」or, not keeping your prostate gland flowing fresh on a regular basis since that would have been very easy to do, and now you have an enlarged, cancerous prostate gland with useless「old meat.」
May refer to the「flow of barbarians」who behave in blundering, reckless, and foolish ways, eating old dried, salted meat such as beef jerky, and may refer to the fact that the conquering northern barbarians arrived in China from regions with large LAKES (that China does not have) such as Ysyk-Kol, Balgash, Alakol, and the largest and oldest LAKE in the world, Baikal, situated near the border between Mongolia and Siberia. Perhaps referring to not being able to travel any great distance on a small lake (as if entering the lake was a blunder) rather than travelling by river. Or that it was a foolish blunder to drink water from a small lake instead of a clean flowing river or stream (brain-eating amoebae may live in those waters), and so on.
[ https://www.livescience.com/66083-why-brain-eating-amoeba-is-deadly.html ]

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: lake
Japanese EDRDG: lake
Unihan extended: a lake; Hubei, Hunan; bluish-green

Used within names (nanori)
うみ　･　み