The etymology of the word "cunt" is that it has Norse/Germanic origins (that's why it sounds hard and strong) and is actually old. From Wikipedia: "The word in its modern meaning is attested in Middle English. Proverbs of Hendyng, a manuscript from some time before 1325, includes the advice:
"Ȝeue þi cunte to cunnig and craue affetir wedding.
(Give your cunt wisely and make [your] demands after the wedding.)"
The use of the word for me is situational. If someone at work calls me a dumb cunt, I'd be offended, but if they called me a ambitious cunt or a smart cunt, it would be a compliment - not only am I "ambitious" or "smart," but I'm strong as well. There is a story I posted here years ago about the time I was given more responsibility at work, including some purchasing decisions handled by a fellow that was retiring. The retiring fellow never sought other bids or negotiated better terms with a particular vendor, in exchange the vendor guy (also older) covering for his mistakes. With the three of us at dinner, the vendor (who treated me like a grandchild and called me "sweetie" sometimes) said it would be the same for me. I chose my words carefully and said, "Not this cunt." (I considered saying pussy or bitch.) It set the tone for the relationship, I got better prices, etc.
As a physical term, "pussy" and "cunt" to refer to the genital region generally, while vagina is a specific place.