Why is a iguanas scientific name called iguana iguana?

Sometimes, there are no answers for these questions. I'm sure that you accidentally read Iguana as what we call it, then the scientific name and thought it was all one, or there could have been a typing error in the thing you read (or I guess if you heard it, there could have been an error in speech). If these aren't good enough answers, then you might as well be asking me why ANYTHING exists...

exactly kinda ...basically most animals scientific names are based on family and genus

a green iguana's family is iguanidae, and the genus is iguana so it would be iguanidae iguana which would be simplified as iguana iguana.