What does Vindolanda mean and how do you know that is what the Romans called this fort?

Vindolanda means white lawns or white fields. We know that the Roman name for the fort was Vindolanda because of an altar set up by the civilians at Vindolanda to the god Vulcan which was found during drainage works in 1914. The altar is on display in the Vindolanda museum. The name Vindolanda has also been discovered on some of the writing tablets.