How to scramble a string of text?

How to implement foo function which works like this:

foo @ "abcdef"

"fdbace"

Steps: "bacdef", "cabdef", "dbacef", "ecabdf", "fdbace"

Reverse the first two letter of the string "abcdef" which will give "bacdef". Then take this as the new string and reverse the first 3 letter. Similarly, proceed for all the characters of the string.