Playing cards have been a popular form of entertainment with both adults and children around the world since ancient times. The number of cards used in an card game has varied from country to country, but in modern times 52 is generally an accepted standard. There are four suits — diamonds, spades, clubs and spades — and the king of spades heads the last.
The origin of the king of spades is French; other European and non-European countries had a variety of different suits and characters. The French re-adapted the spades suit from the suit of leaves that was used in German playing cards. It was common for the suits to represent historical characters or the prevailing social class. While the German leaves suit was a representation of the middle class, the French spade suit came to represent the spearheads of the aristocratic knights.
The French card designers were the first to identify the royals in the suits with historical or existing royal personages. The cards usually carried the name of the royal personage, but there was no standard consistency here. As different designers had different preferences or loyalties, it was quite normal for different cards to represent different royals. King David was a popular choice as the king of spades, and was shown with a lyre and a sword. In fortune telling, where royal personages were not a requirement, the king of spades was often interpreted as an intelligent, difficult character, most often a lawyer with shaky ethics.
The reason that the French king of spades became the standard in playing cards is because of the ingenuity and enterprise of the French card-makers. At a time when printing was a laborious and expensive process, they devised a quick way of producing the cards. Instead of engraving each card separately, they carved the designs of the king, queen and knave on wood blocks or copper plates and used these for all the suits. The symbols of the suits were added on later with stencils.
The French printing process was time-saving and it allowed the French card-makers to produce cards at a faster and cheaper rate than their European counterparts. As a result, it became possible for ordinary people to afford playing cards, and, as more and more people bought the inexpensive French cards and learned to play with the French suits, these then began to be the norm on the European continent. The rest of the world soon followed the fashion.