OK the absolutely easiest way to get this without being in an active battle.
Play the 1st level in story mode and get to the gem pile at the end. Don't enter a word to smash it, just keep spamming
to change your letters. As you're not in an active battle you don't lose health and so it saves you having to do it in the heat of the game.
Yes it would probably come from natural play but doing the above it can be one of your 1st achievements in the game and it's out of the way for less than 30 seconds effort.