Chinese sources explain that this glyph is a simplified variant of "to defecate EXCREMENT" (see 屙 as the 'nook and cranny between buttocks,' quite literally the "hole in ass" as it were). Note that in English also, excretion of fecal matter is referred to as a BOWEL MOVEMENT, literally「quick movement with orifice」as these elements depict.「Stiff end-to-end」when used as a stand-alone glyph refers to a CORPSE, a reference to becoming stiff meat during the onset of rigor mortis. Most corpses will also defecate EXCREMENT and urine as the various sphincter muscle sets relax. Sphincters are ringlike muscles that normally maintains constriction of a body passage or orifice that relaxes as required by normal physiological functioning, and also at death. Male corpses can manifest a priapism, an erection after death, known as a 'death erection' or 'terminal erection' observed in some corpses of men who have been executed.
　Merges「erection」and「end-to-end」or「orifice」and means the BUTTOCKS and GROIN and GENITAL region with the ANUS at the base end of an erection and the glans at the other, the male genitals.「Erect quick movements with orifice」are a candid reference to copulatory actions in one orifice or another, but more often than not refer to anal coitus as a reference with these Chinese glyphs.
　「Erect, quick movements」with the tip inserted into an「orifice」also refers to necrophilia, one popular manner of defiling an enemy CORPSE after a battle, or during the battle if a lull has occurred in the nearby hand-to-hand fighting, prior to decapitation and emasculation of the fallen, or slicing off the ears and nose, or scalping, or some other form of desecration.
　A 'fresh corpse' (not an oxymoron) also has the known tendency to SLUMP somewhat, prior to the onset of rigor mortis. Often FECES AND URINE are excreted spontaneously from the orifices of a CORPSE as the sphincters relax, prior to the onset of rigor mortis and prior to the onset of necrophiliacs. Furthermore, often FECES AND URINE are EXCRETED spontaneously from the GENITAL ORIFICES of a person SLUMPING, SQUATTING while expecting to soon become a CORPSE, due to terror, fear, shock and awe, or as a means of PRETENDING TO BE DEAD as the listed Unihan meaning (something to recall in some circumstances, to be sure). Based on physiology, SQUAT is the correct position human beings should assume to defecate EXCREMENT (see 屙)
　　[　https://slate.com/technology/2010/08/how-bathroom-posture-affects-your-health.html 2023-05-17　]　
　And everyone did so before the invention of the sit-down toilet, formerly used only by royals and sick folks…squatting-style toilets are still ubiquitous in Asia, although losing favor.
　Despite what external sources suggest, it seems that this element has nothing to do with flags or banners…see all the Used-In glyphs.
　「A death erection, angel lust, or terminal erection is a post-mortem erection, technically a priapism, observed in the corpses of men who have been executed, particularly by hanging. The phenomenon has been attributed to pressure on the cerebellum created by the noose. Spinal cord injuries are known to be associated with priapism. Injuries to the cerebellum or spinal cord are often associated with priapism in living patients. Death by hanging, whether an execution or a suicide, has been observed to affect the genitals of both men and women. In women, the labia and clitoris will become engorged and there may be a discharge of blood from the vagina. In men, 'a more or less complete state of erection of the penis, with discharge of urine, mucus or prostatic fluid is a frequent occurrence…present in one case in three.' Other causes of death may also result in these effects, including fatal gunshot wounds to the brain, damage to major blood vessels, and violent death by poisoning. A postmortem priapism is an indicator that death was likely swift and violent.」
　　[　https://en.wikipedia.org/wiki/Death_erection 2013-09-26　]　

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: corpse; variant of 屍
Japanese: corpse
Unihan extended: corpse; to impersonate the dead; to preside
EDRDG: corpse; remains; flag radical (no. 44)