Johannes is the Latin form of the personal name that usually appears as "John" in English language contexts. It is a variant of the Greek name Ιωάννης (Ioannes), itself derived from the Hebrew name Yehochanan meaning "Yahweh is gracious". The name became popular in Northern Europe, especially in Germany. Common German variants for Johannes are Johann, Hans (diminutized to Hänschen or Hänsel, known from "Hansel and Gretel", a fairy tale by the Grimm brothers), Hannes, Jens (from Danish) and Jan (from Dutch).
Common English variants for Johannes are Johanan, John, Johnny. In French is Jean, in Spanish Juan, in Portuguese is João, in Catalan is Joan, in Russian - Иван (Ivan), in Lithuanian - Jonas, in Romanian is Ion and in Italian is Giovanni. In Indonesia, it is Yohanes. The Irish or Scottish Gaelic equivalent is Eoghan or Eóin, and in Welsh it is Ieuan or Ifan, anglicized as "Evan". In Estonian Juhan, Jaan, Jaanus, Joonas and Hannes do come from the same root; Juss and Juku are the familiar names for Johannes.
Read more about Johannes: People Named Johannes