I can't speak for all anal-erotic males, as to how they might have become fanny-finger fans. For me, the phenomenon goes back to delicious childhood experiences; at least, they seem to have been delicious. At the same time, it wasn't quite like the eating ice cream-type of delicious, because I can remember fighting the promise of the suppository-experience(I would never fight the promise of an ice cream cone) .
To my mother, few things in life were as important as a regular bowel movement. The question of the day, almost every day, was, "When did you last make a doody?" Unevacuated stool was considered poison which had to be gotten out, or dire consequences unspoken were sure to occur, like maybe death by bellyache. Mother could help, though. Healing could be found in a small jar in the medicine cabinet. "Infant suppositories" were of the elongated type then. They curved slightly toward the rounded end that was to be inserted first. They came a dozen to the jar, with a picture of a white-coated pharmacist on the label, standing behind a table on which rested a mortar and pestle, the symbols of his trade.
The favorite position for administering was over-the-lap, with mother sitting on the toilet seat, the little jar next to her. With me over her knees, first my trousers were lowered to my ankles, and then mother would pull my briefs down over my little butt, expositing the cheeks to her view, to await the rude manipulations to follow. Then with her right hand she would fish out one of the little magic cylinders, while with the finger and thumb of her left, she would part the little cheeks, revealing my tight little rosebud. I, of course, could not see her deftly handling my little tush, could only feel the intense sensations she was causing as she fingered the spot where all my erotic sensation was so concentrated.
Then suddenly the slippery little projectile was there, at the tiny entrance to my rectum, and waves of indescribable sensations would race through me as I could feel it slipping in past the little ring, followed by a finger pushing it up, up further into the rectum. Even at this tender age(I couldn't have been more than five of six) my tiny penis stood erect, pushed outward in the storm of overwhelming feelings that flooded my consciousness in the moment of insertion. As my memory serves me, the wait was not long before the cure for all my ailments occurred. In the meantime, my little anus would contract, an act which I recall as bringing a pleasurable sensation of its own - the feeling of having a full rectum and withholding its contents.
Time went by. At age ten or so I bravely went up to the pharmacist and asked for a jar of infant suppositories. I'm sure he knew he was selling me a sex toy. I secreted the little jar in my dresser drawer and awaited the magic moment when I could be alone in my room. In seclusion I opened the jar. Savoring each step, I gave myself first one, then a second suppository. The feelings were indescribably wonderful. I had learned to masturbate.
I grew up, but part of me never grew up. Even as I continued to recall the delicious sensations of the childhood suppository experience, I could feel the storms of erotic sensation build as I recreated the memory of being over mother's lap, at the moment of insertion. I reinforced the fantasy by finding objects to insert up my asshole; a rectal thermometer, an enema nozzle, finally suppositories themselves. It took courage to go into the drugstore and buy those things, thinking that the girl at the checkout counter could picture me masturbating while shoving a suppository up my ass. I countered my embarrassment with enjoyment of her supposed fantasy. I wondered why, as a six year old I could have resisted such a wonderful experience as having mother give me a suppository.
I studied psychology, and I pondered, and finally I realized that a six year old can't handle the erotic feelings that she unwittingly forced upon me. I think it was unwitting. Did mother experience a thrill as she gave me a suppository? Did it stimulate her own anal longings, perhaps? I was being goosed erotically, a powerless victim being mini-raped by my own mother, forcefully shoving an object into my sensitive rear opening. Having concluded that my mother's anal manipulations under the guise of a remedy were a mild form of rape, have I become angry? Do I ponder some form of revenge? No, not at all.
What I ponder is my wish to become a little child again and have a woman put me over her lap, pull down my pants and send waves of erotic sensations through me by shoving a slippery object way, way up into my rectal opening. But now, you see, I could handle the delicious sensations, and I would no longer have any need to resist. And then, after my having assumed the passive role we could switch roles, and this would be another way for me to master these early experiences. No longer the "victim", I could become the active partner, and get off by creating, for my fortunate partner, the delightful, delectable suppository experience.
And so you see, this is the way I became the anal-erotic man I am today - and, here is the catch. How do I find this anal-erotic woman who will recreate my childhood memories, and let me then fulfill my other fantasy, by lying over my lap as I explore her little bum hole? Does she exist for me, my partner in ass-play, my enemate, my Suppository Suzy? Oh Mommy, where are you now, now that I need you? I haven't had a bowel movement in seven days, maybe eight, and if I don't find her, I may never shit again!
But then - Oh, shove it!