Isaac: the son of Abraham and Sarah, the promised heir and second of Israel's three founding fathers.
Isaac is the long-awaited son God promised to Abraham and Sarah in their old age, and after Abraham he is the second of the three patriarchs Israel traces itself back to. His life fills much of Genesis: the near-sacrifice on Mount Moriah, his marriage to Rebekah, and the birth of his sons Esau and Jacob.
The name is a small Hebrew sentence meaning "he laughs" or "he will laugh," and the Genesis story turns that meaning into a running thread. Abraham laughs when God promises the child (Genesis 17:17), Sarah laughs in disbelief and is questioned about it (Genesis 18:12-15), and when the boy is finally born Sarah says God has made laughter for her (Genesis 21:6). The same wordplay resurfaces later when Isaac is seen "laughing" with Rebekah (Genesis 26:8).
Because he is remembered as the middle link in the chain of promise, his name settles into a fixed formula that echoes through the rest of the Bible: the God of Abraham, of Isaac, and of Jacob. In those passages the name is less about the man's biography than about the covenant God keeps across the generations.