The act of inserting one and/or two hand into the vagina/rectum in a woman or in the case of a man, one and/or two hand in the rectum. This is a process that requires extremely sensitive care and a whole lot of lubricate. It is also a process that is not only popular among gays as many had pointed out. It has been perform by women and men: homosexual, straight, or otherwise. Though the word "popular" isn't something that can be thrown out and about. There are many form in which fisting can be done. Highlight: Take your time. Rushing, jamming, pushing, violating, uppercutting, sticking it up there, shoving, throwing, ramming, jabbing and anything of the like without preparation is extremely painful. Never mind that, it's never pleasant when something like that is done.
It was the most uncomfortable feeling of being stretch internally but Pat was careful in fisting Angel, got to do his kink, and Angel benefits from it.
A persona created by J.K. Rowling who played the role of a professor in Hogwarts, a spy, a traitor, and a man with a burden. With his hand force, in situations where many other would have failed in doing what they had to do, he succeed thus continue his chain of regrets and guilt. Hence, his legend of battyness/vampiric/cruelity his person goes on.
Snarky and harsh Snape can be, but in the era where he grew and lived, it is often time the best shield and sword.