Old, old saying because it's actually witch's teat. Teats, dugs. Old timey words for boobs make me laugh in a way that "boobs" will make future generations giggle. The internet says that it has something to with courts and accusers searching for the witch's mark, which was often on the boob. So the accused had to pull their tits out for getting checked and that made them cold? I'm more interested in the idea of getting marked by the devil by having him suckle on your tit. With some of the men I've been with, I'm about to start checking myself for marks! (I mean this in the hottest way possible, actually.) But, you know, it's fucking cold out!
THAT being said, witches are slutty. Historically speaking, sexually liberated women were often the first to be accused of witchcraft. I vividly remember catching the imagery when I read Macbeth and the three witches were talking about draining men dry as hay. Rarr! Sort of like the first time I read Songs of Solomon after being told it was dirty and thinking "oh...wow...I see." Honey. Milk. Antelopes. Oh. Ohhhh.
So yeah. Exhibitionism. Fucking the Devil. Group sex. Seduction powers. Sign me up for witch-hood, please. Witch-hunts aren't as violent these days, so I think I might be alright.