This word originates from the word thicc. The extra four c's and one k are used to make the word more classy and to boost up others self esteem. It can also be used to describe something that is quite large in a positive way or to be used to describe oneself.
Sarah felt depressed in the dress she wore but I called her thicccck with four c's and a k to cheer her up. She turned around with a smile about her positive body.