[Elements vary by font] Some external sources describe this element as「the mother radical」and while quite similar, it nonetheless contains some significant variations from 母「mother」as listed in Chinese sources.
　Meaning DO NOT, BE NOT, MUST NOT DO all seem NOT to reference motherhood at all, but instead exhort everyone NOT TO「perforate, penetrate」whilst schtupping (ejaculation into a birth canal or other attainable orifice) the no-longer-integrated foot of a dynastic Chinese service provider—or better yet, forego the practice completely. Just look at the source elements for confirmation.
　FOOT BINDING was:
　「…[T]he custom of applying painfully tight binding to the feet of young girls to prevent further growth. …To enable the size of the feet to be reduced, the toes on each foot were curled under, then pressed with great force downwards and squeezed into the sole of the foot until the toes broke. The broken toes were held tightly against the sole of the foot while the foot was then drawn down straight with the leg and the arch forcibly broken. …The tightness of the binding meant that the circulation in the feet was faulty, and the circulation to the toes was almost cut off, so any injuries to the toes were unlikely to heal and were likely to gradually worsen and lead to infected toes and rotting flesh. If the infection in the feet and toes entered the bones, it could cause them to soften, which could result in toes dropping off. Although, this was seen as a benefit because the feet could then be bound even more tightly. Girls whose toes were more fleshy would sometimes have shards of glass or pieces of broken tiles inserted within the binding next to her feet and between her toes to cause injury and introduce infection deliberately. Disease inevitably followed infection, meaning that death from septic shock could result from foot-binding, and a surviving girl was more at risk for medical problems as she grew older. …Bound feet were once considered intensely erotic in Chinese culture…. Qing Dynasty sex manuals listed 48 different ways of playing with women's bound feet.」
　　[　https://en.wikipedia.org/wiki/Foot_binding 2012-12-17　]　
　If there were NOT mothers, there would be no humans, nor most other animal species, in just a few short decades. Moreover, associations with this glyph used as an element in other glyphs as being frequently a person of reprehensible morals, an immoral adulterer (are there other kinds?), cruel, malicious, poison, venomous, toxic and harmful do not seem to apply to most mothers, human or otherwise let's hope, but do in fact seem highly applicable to schtupping (ejaculation into a birth canal or other attainable orifice) with a no-longer-integrated foot. Furthermore, the substitution in glyph fonts of this element in place of 'mother' is seen in Japanese fonts as a variant, but not traditional Chinese fonts, indicating that there remains some difference in the two meanings in spite of much similarity of usage, appearance, and potentially some deliberate obfuscation of the original glyph elements. Nonetheless, some women who have become mothers can actually be pretty bad.
　Arguably, the elements could also be「penetration, perforation, distorted perverted screwing」within「loose no-longer-integrated foot」of a female service provider: DO NOT…MUST NOT…BE NOT that way.「Loose and flapping」with「erect rod」or「screwing」(inner elements vary by font) enclosed by「tense gasping with no-longer-integrated foot」depict use of a no-longer-integrated foot being grasped and used as a masturbatory aid, a SUPPORT BRACE in two ways: as surface friction and pressure to stimulate the glans and penile shaft, and, as the client's hands supporting and bracing the service provider's raw foot meat (feel free to research and view some Chinese erotic art if you cannot believe this scenario). …while some service providers were mothers, and while some mothers who were not service providers had no-longer-integrated feet in China, one cannot definitely link motherhood to grasping busted feet for masturbation by males. Rather, meanings of DO NOT, BE NOT, MUST NOT DO all seem to reference not becoming, or engaging with, a no-longer-integrated footed service provider. In other words, DO NOT, BE NOT, MUST NOT engage with or become personally a sexualized object, a thing, a piece of meat, a sex machine, a sex animal herd meat asset fuckbunny.
　「Bound feet were once considered intensely erotic in Chinese culture. …The process was started before the arch of the foot had a chance to develop fully, usually between the ages of 2 and 5. …Qing Dynasty sex manuals listed 48 different ways of playing with women's [no-longer-integrated] bound feet」(after removing the binding cloths, of course)
　　[　https://en.wikipedia.org/wiki/Foot_binding 2012-12-17　]　
　Not coincidentally perhaps, 女, 母, and 毌 as female, mother, and penetrated (respectively) all utilize the same basic elements with slight variations, but arguably any mother in the old days must have been a female who was penetrated at some point in time and space, barring an immaculate conception parthenogenetically. Both service providers and concubines depreciated in value as sexual objects after motherhood, so perhaps DO NOT, MUST NOT, BE NOT A MOTHER might apply specifically in that limited sense to anyone「with loose no-longer-integrated foot that is penetrated or perforated with perverted screwing as a support brace.」…and like it or not, both service providers and concubines were deliberately sexualized objects, converted into chunks of meat by sacrificing the ability to stand or walk normally for their entire lives, periodically re-dis-integrating and pulverizing the arch bones of both feet. Nonetheless, this glyph logically cannot be deprecating the value of motherhood as an institution, as long as she keeps her「loosely grasping hands」to herself, naturally.

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: no; don't
Japanese: must not, do not
Unihan extended: do not; not
EDRDG: do not; must not; be not; mother radical (no. 80)