According to Shogakukan's Nihonkokugodaijiten dictionary, ken arrived in Kyuushuu in 1642, spread to the Osaka area by around the Edo period, and spread to Edo (now Tokyo) by about the Kyouhou period (around the 1720’s). Because it first arrived in Nagasaki, it was sometimes called Nagasakiken or Kiyouken (Kiyou being the old name for Nagasaki).
Honken was played between two people, each of whom would simultaneously extend 0 to 5 fingers of one hand, and at the same time predict the total number of fingers. Whoever correctly predicted the number of fingers shown was the winner. Originally, this was a game played in drinking places as a way to determine who bought the drinks or who had to take a drink. While I was in the Navy, we played a variation of this to decide who would go buy soft drinks for everyone. Each person had three paper clips behind his back. Each person would choose from one to three clips and hold them in front in a closed fist and each player would predict the total number of clips in all players’ hands. On command, all players opened their hands. The eventual loser went for the drinks.
Various kens were created, such as willow-ken, tail-up ken, deep-river ken, strip ken, circular ken, hand-up ken, follow-me ken, blindfold ken, and fists-together ken. What is called Janken comes from the guu, choki, paa or rock, scissors, paper sansukumi way of thinking. Sansukumi is expounded in the book called the Kan'inshi, which describes how the snake fears the slug, the slug fears the frog, and the frog fears the snake. Each of the three animals holds the others in check, so that the three cannot move, the same relationship as between rock, paper, and scissors. When this idea propagated to the honken and other ken (hand) games, games like Janken resulted. The jankens of the Edo period included Shouyaken and Mushiken.