The fig is a gesture made with the hand in a fist and the thumb between the index and middle fingers. It represents the feamle genitalia, as the digitus impudicus (or bird) represents the male.

there is a wonderful scene in the movie version of "Wives and Lovers" (i haven't yet read the book), of picnic, with figs on the menu.

one of the gentlemen (i saw this movie more than 30 years ago, and the names of the characters have faded from memory, but this scene is still sharply etched!) picks up a fig, and compares it to a woman.

on the bottom of the fig, he traces the natural lines of the fruit, and compares them to the delta of venus, and then cupping the fig in his hand, he gentle parts the fig.. and exposes the moist suculent flesh inside, which he then presses to his mouth, and using his tongue, he devours the flesh --i was adult (nominally!--but still a teenager) and the scene had me squirming in my seat.

since then, i have always understood why the fist, with the index finger and middle finger split by the thumb is called a fig, and exactly what was meant by the gesture!

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meanwhile just speculating, could it be that figs, a common commodity in much of southern europe, where the 'tokens' of the day?

for years, a valueless items, or information (in NYC) have been greeted with the comeback "Yeah, and that and token will get you on the subway" --
could it be figs, were so common, (and so cheap) that to not give a fig, was to not give something that could be purchaced for less than a penny (or the local equivient of a penny)? i can buy dried figs (a bunch of 20 strung together to form a ring, on sale sometimes as cheap as 2 rings for a $1. --40 figs for $1. (and these are imported!)
how much cheaper they must have been locally.

perhaps figs (delicious as they are!) were just a term for "cheap easily aquired goods" and to not give a fig, was a way of saying something was worthless.