Talents are an extremely common occurrence for both character and players alike. So why talk about them in your character's backstory? Aside from showing some of your character's creative accomplishments, there isn't much reason.
NOT TRUE!! There is always a reason. What if your character has a unique way of accomplishing that talent. Or maybe that end goal can only be accomplished by your character's "hidden talent."
Imagine, if you will, a puzzle lock within your game that can only be solved with music. But for some reason (only your DM/GM knows for sure), the music cannot be created via your mouth or any standard instrument. What do you do? Your character uses a Nose Flute, of course, and your character just happens to have a hidden talent that allows them to do so. Or maybe your character is enjoying some downtime at a local tavern and really wants to impress the barmaid she just met. How does your gnome barbarian impress another woman? By tying knots in cherry stems with only her tongue.
Hidden talents can come in seemingly endless varieties and they are a great way to add some fun and hilarity to your games. When thinking about hidden talents to give your character, start by exploring a number of normal talents. Then all you have to do is give your character an unusual way of accomplishing that talent.
Maybe your character is asked to remember what they had for breakfast on a certain day 18 years ago, but the don't have a photographic memory. What if your character has a mathematical hidden talent that allows them to perform an extremely complex equation which comes up with the right answer, thus allowing them to discover that the person asking the question is actually their long lost mother.
Have fun with your cherry stems!!