Hand shake- it's origins are noted to Ancient Greece, where it was a way of saying "I'm unarmed". People held their hands and each other patted for hidden weapons.

Thumbs up- they say it was a way the crowd of gladiator fights decided the fate of the fallen warrior. Up until 1872 it was unclear if thumb up, down or sideways saved the life, in that year Frenchman Jean-Léon Gérôme painted gladiators where he guessed the good way is up, and since then thumbs up is something good and down is bad.

Salute- there are many opinions, with the most popular being knight opening their helmets showing their faces to their king or other ruler. Other options include covering the eyes pretending the ruler is like the sun or taking off hat in a gesture of respect.

Middle finger- you know what it means, and it means that probably by resemblance to you-know-what; but British show two fingers with palm to themselves. The English sign is said to come from the battle of Agincourt (1415) where it was used to show the French that British archers have fingers to shoot them full of arrows. It was because when Englishmen invented the longbow, French still used the much worse short bow and feared opposing archers; and every archer the French caught got their fingers cut off, so it's a way of saying "we will f*ck you up".

Nazi salute- Hitler took this salute, used in Germany even now (seldom, by people hating immigrants), from Italians who were the prototype of Nazis- Fascists. Italians claimed it was the way Romans saluted, but that is a lie because no one knows exactly how a roman salute looked like; Fascists claimed the salute can be seen on this painting Oath of the Horatii by Jacques Louis David- but as you can see they're NOT saluting but holding hands out to grab some swords.

Victory- the sign comes from Belgium, in 1941 Victor de Laveleye said to show this to Germans as a way so say "we are not defeated, we wait for the right moment to strike". Fun fact: Winston Churchill showed this sign both palms out and palms to himself before someone told him the second one means "f*ck you".

O.k.- it is said to be short for "all correct", or the nickname for Martin Van Buren, it is also said it comes from the Vietnam War and meant "zero killed". Fun fact: in some countries it means "you're a nobody" or even "f*ck you in the a**".

High five- it is a continuation of "low five" and is said to be first made by Dusty Baker and Glenn Burke in October 2nd 1977.