Suppose all 5!=120 permutations of dhoni are listed in 
alphabetical order, numbered #1 through #120.  

For instance. in the list, arrangement #1 is dhino and 
arrangement #120 is onihd

Since 5! = 5*4!, we can think of it divided into 5 groups of 4!
(that is, 24) permutations each. 
the 1st 4! begin with "d", they are #1 through #24 in the list.
the 2nd 4! begin with "h", they are #25 through #48 in the list. 
the 3rd 4! begin with "i", they are #49 through #72 in the list.

So the word which is #73 in the list is the first one that begins 
with "n", which is ndhio 

Edwin