Spelling a word backwards that isn't a palindrome.

[Lexicon]

I'm new here and I'm a bit of a writer. I was wondering if a word spelled backward has a name, for the concept I mean. Now, I don't mean a palidrome; the same backwards and forwards.

For example: Warning into Gninraw

What is that called? Is there a term for a simple backwards word?

[Tdol]

I have seen called 'mirror writing' when talking about Leonardo da Vinci's diaries.

[Mr R Walkowiak]

I have heard of 'backslang' hence yob from boy.