Why do you suppose a guitar has six strings?

I wonder why a guitar has six strings. It seems to me, given that chording is a common way of using the instrument, that there might be four, maybe five strings. Of course, I know that a ukelele has four. And I know that a piano has 88 keys. But there is something sort of intimate about the guitar players left hand(or right if you are Paul McCartney) and the number of strings. Four fingers to play with, maybe the thumb if you wrap around, why not four or five strings? Disclosure, I play guitar and am pretty good, so I am not really asking for a guitar lesson. What is the history of six strings?