Putting two fingers up in the shape of a "V" behind your friend's head has a dark origin.
<ul>
<li> In the Middle Ages, the bunny ear gesture was used to shame a man whose wife was unfaithful.</li>
<li>The hand sign may also symbolise donkey ears - a common insult in Medieval times.</li>
</ul>

Bunny ears

<ul>
<li>Applause dates back to ancient times.</li>
<li>In Western culture, clapping originated in the ancient Roman theatre.</li>
<li>From there, Roman politicians used the applause to gauge their popularity and approval based on how much applause they received.</li>
<li>Applause was also used as a way to collect data and determine leadership value.</li>
</ul>

Clapping

<ul>
<li>One theory claims that on Oct 2, 1977, the high five was created when Los Angeles Dodger Glenn Burke thrust his hand over his head to greet another Dodgers player, Dusty Baker, and Baker smacked it.</li>
<li>The other theory is that basketball player Derek Smith invented the high five during the 1978-79 season. Another player, Wiley Brown, tried to give Smith a low five, but Smith asked for one high up instead.</li>
</ul>

High five

The hand signs' meaning is believed to date back to ancient times, with the Greeks using it when referencing male genitalia. The Romans called it the "shameless finger."
Its earliest documentation in the U.S. was in 1886 when a pitcher for the Boston Beaneaters " flipped the bird" in a photograph with the team's rivals.

The middle finger

The original gesture was an ancient pagan custom that demanded two people to cross fingers - the idea that wishes would be kept safe until they came true.
Early Christians often crossed their fingers when faced with persecution to invoke the power of Christ's crucifixion or to absolve themselves from sin. Some would cross fingers with fellow Christians before Mass to form the symbol of the ichthus.

Crossed fingers

One of the earliest depictions in art of a handshake is from the 9th century B.C. Homer mentioned a handshake in The Odyssey a century or two later.
<ul>
<li>One theory about the origin of the handshake suggests that showing someone your empty, weapon-free palm portrays peaceful intentions. The shaking motion would dislodge any hidden weapons.</li>
<li>Another theory suggests the clasping motion symbolises good faith and a sacred bond.</li>
</ul>

Handshake origin

In ancient Rome, referees originally used these gestures to decide if a gladiator should live or die. However, thumbs up meant death, and pressing your thumb down on your fist meant life.
In 1917, in a book titled Over the Top, Arthur Guy Empey explained that U.K. soldiers used the phrase thumbs-up to indicate that all was well.

Thumbs-up and thumbs-down

The "V" sign can be used as a symbol of peace or an insult. In the U.K., if your palm is facing yourself while you're making the sign, it's the same as using your middle finger in the U.S. If your palm is facing outward, the sign simply means the number two.
During WWII, the V sign (with your palm facing outward) was used to signify "victory.", After the 1960s, the hand sign began to be associated with "peace" by American and British youths.

The V sign

This sign has a lot of possible origins. The popularisation is attributed to Ronnie James Dio in the 1970s. Dio says his Italian grandmother inspired him to pick up on the "corna" gesture to ward off the "evil eye" and bad luck.
His grandmother might have been inspired by the 1897 novel Dracula, which mentions characters using the sign to protect themselves from the evil eye.