The English word Vandal or vandal comes from the Latin form, Vandalus which in Germanic was Wandal.2. Etymology: from Latin, Vandalus (s), Vandali (pl); a name of Teutonic origin; probably literally meaning "wanderers" and related to German wandeln, "to wander".
2. Anyone who willfully or ignorantly destroys or mars something beautiful or valuable.
Although the Vandals did their share of raiding and plundering, they don't seem to have engaged in trashing and plundering as indicated by the modern usage of vandal.
The Vandals did acquire a reputation for their name to be used as a lower-cased term meaning, "anyone who willfully or maliciously defaces or destroys public or private property".
There does not seem to be in the story of the capture of Rome by the Vandals any justification for the charge of willful and objectless destruction of public buildings which is implied in the word "vandalism".
It is probable that this charge grew out of the fierce persecution which was carried on by [the Vandal king] Gaiseric and his son against the Catholic Christians, and which is the darkest stain on their characters.