Isaak

Isaak is an established form of Isaac used in Greek, Russian, and German traditions. The name ultimately comes from Hebrew Yitzhak, meaning he will laugh. In Genesis, the promise of Isaac's birth is connected with the laughter of his parents, Abraham and Sarah, giving that meaning a central place in the biblical story.

The final k distinguishes Isaak from the familiar English Isaac without changing the underlying name. Pronunciation varies among the languages that use it, so it does not have one universal English sound guide. Families may choose Isaak to retain an ancestral spelling while keeping a clear connection with the wider Isaac family.