It is used for unleavened baking, or as a thickener.
To make cassava flour, cassava roots are fermented or boiled, then dried and ground into a flour.
No insects, not even cockroaches, will eat cassava flour.
When a recipe calls for cassava flour as a thickener, you can try using toasted bread-crumbs, or just plain old all-purpose flour. Use double the amount per amount of cassava flour called for.
Columbus’s diaries mention his eating bread made from cassava in the New World.