「Alcohol first used」is a glass raised in a TOAST to the host by guests, a Chinese meaning, but similar to the first kampai in Japanese. And「cock meat first used」was likely a reason for「bottoms up」and raising a glass in TOASTING.
　At a formal meal, guests are served a small glass of a sour or citrus beverage that serves to stimulate appetite and aid digestion. Vinegar previously was wine (literally「vine」or grapes, and「gar」or soured). When producing alcohol during fermentation, yeast must be deprived of oxygen, and if so, ethyl alcohol and carbon dioxide are the byproducts of yeast digesting sugars. However, if oxygen is permitted to contact the yeast, these little fungi will produce what eventually becomes VINEGAR instead (acetic acid has the same molecular structure as alcohol but with oxygen atoms added). So, if you「first used wine」but did not seal the jar well, or simply waited a long time after formerly opening the jar and letting in some air with oxygen and perhaps some additional living yeast cells drifting in the air, any living yeast fungi in the wine would then start producing acetyl-CoA that eventually becomes vinegar instead, and your beverage that「first was used as wine alcohol」will change to VINEGAR,「wine while doing something else.」The lesson here is to finish up each open bottle in a relatively short period of time (preferred), or fortify your wine with distilled alcohol to a level that kills all yeast organisms and ceases production of acetyl-CoA (also preferred). A tank of pressurized carbon dioxide dispensed by rubber hose added into the bottle before re-corking also helps, but that may not have been an option for many cave folks. Related glyph with same meaning is「alcohol from long ago.」
　One's「cock meat doing something else」refers to SOURING, CHANGING INTO ACID, spewing venom instead of sweetness, losing the sugar content.
　One's「cock meat in first use」is more than likely EXPRESSING JUICES BY SQUEEZING rather than by any other means.
　「Cock, wine」with「first use」「doing something else.」…together meaning VINEGAR, but more: eating the chicken「cock meat」is「doing something else」besides providing you with nourishment and calories…the best defense against stomach acid reflux, particularly when drinking wine, is to prevent it in the first place by「first using chicken」as part of your meal　[　https://www.ucihealth.org/blog/2023/03/gerd-friendly-recipes 2023-05-17　]　

Modern definitions (that generally disregard history) …excluding politically incorrect concepts and other meanings deemed offensive today; may list only pigeonholed definitions, euphemisms, or meaningless mnemonics)
Chinese: toast to host by guest; variant of 醋
Japanese: vinegar
Unihan extended: toast one's host with wine; to express juice by pressing
EDRDG: vinegar; sour; acid; tart