It was used occasionally before that, for example the old English poem "Widsith" (~10th century) refers to Scandinavian raiders as "wicinga cynn" or Viking kin.

It was used occasionally before that, for example the old English poem "Widsith" (~10th century) refers to Scandinavian raiders as "wicinga cynn" or Viking kin. But it wasn't a common appellation and may have referred more to their status as sea raiders or pirates.