Just as general feedback, using the same characters to designate the variable and the index in this example is confusing. Using a different character such as c = "cats" for "t" illustrates the relationship with no cross-over.
The variable 'c' could have been anything. if you don't like it being 'c' then make it 'letter'. The variable name does not matter, Python only checks to see if it obeys preset laws like it can't be two separate words. It can be 'JoinedWords' or 'joined_words'. Hope this helps.