To be real I think that term has gone through so many evolutionary changes since it was first coined that now in 2024 virtually any definition someone has will have 200 people who will say "yes that's what I always thought it meant". I'm serious about that because way, way back in ancient times, when I first heard the term it simply referred to any young woman you would see in public with a baby or small child/ren who was still gorgeous and would draw the reaction "hello mother, want another?". A very short time after that in my business it had already gone through it's first definition "evolution" when the adult studios wanted to use the theme in titles and scripts. By then the term applied to any woman who appeared too old to get away with a fresh face title (teen in today's terms), yet she was still porn star gorgeous. She'd be labeled a MILF and her role as someone's nanny, older sister, mom, maid, boss, wtf-ever would be written into the script (yes, we used scripts back in porn movies then). It wasn't too long after that period that the term picked up so many side definitions it could apply to anyone anymore, which means in truth today it just means whatever the hell you'd like it to mean.
Another side note here, since were talking definitions here. By our professional studio standards, from the 70's to late 90's, virtually nothing you see on any of the web sites, pay sites, myfriends sites, onlyfans sites...none of it, would meet our definition of a useable or releasable product for the public. One after another they're all an endless string of wham-bam fuck shorts. Half of them, I swear, were shot with a cell phone. Pick a kink and start the fucking. Cum and the end. That for me, knowing what they could be filming with some of these gorgeous newcomers is not only boring as fuck but an incredible waste of beauty and talent. But to each his own, I guess. We old folks don't know nothin...