Why is olaf called Olaf in "Frozen"?

Because olaf means family heirloom in Danish, and he is a cute little snowman in the movie, so he was named Olaf.

Olaba loves warm hugs and was born unexpectedly through the magic of Elsa. Olaf is the friendliest snowman in history. His innocent and cheerful personality is endearing; his weird ability allows him to separate his body and head from time to time, making the scene awkward and funny. Olaf also has the most whimsical dream in the world - he looks forward to welcoming the warm wind and scorching sun of summer.

The symbol of Olaf:

Olaf actually symbolizes Elsa and Anna, the sisters’ childhood memories and friendship. In the first episode of "Frozen", when Elsa was depressed and ran away from the Kingdom of Arendelle, she accidentally used ice and snow magic to create a living snowman named Olaf. Therefore, when Elsa was trapped by the mysterious magical power of Atohallan in "Frozen 2" and lost her life, Olaf also disappeared with her.