In A Feast for Crows, Cat of the Canals works in the fish markets in Braavos. She is taught and has to be very rugged because of the nature of the place - being filled with sailors and rugged men so on.
She learns to show people 'the fig' which is described as some sort of rude hand gesture; I'm assuming that it's the rude finger.
Some details: [A Feast for Crows spoilers]
Cat is actually Arya Stark
Here are a couple of excerpts from the book.
"... a coarse jumble of words and phrases from a dozen languages, accompanied by hand signs and gestures, most of them insulting. Those were the ones that Cat liked best. Any man who bothered her was apt to see the fig ..."
"... They bought clams and cockles from her, told her true tales of Braavos and lies about their lives, and laughed at the way she talked when she tried to speak Braavosi. She never let that trouble her. Instead, she showed them all the fig ..."
-A Song of Ice and Fire: A Feast for Crows, Cat of the Canals.
Some information I have found is:
Is this correct? What does 'the fig' hand gesture look like?