Last n words from a string in bash

I have a string containing many (the total number varies) words, and I need to get last 10 of them. How do I do it? I'm looking at awk, grep and cut but nothing really comes to mind.

An example (although it seems to me that the question is clear):

aaa bda fdkfj fds fsd ... dsad dsas dsad zrthd shshh

I want the last 10 words of this string.

Again, the total number of words in the initial string isn't defined.