Didn't the Vikings originate in Denmark? I'm sure they eventually populated Sweden and Norway.
No. Danish vikings raided the continent and England, Norweigan Vikings raided mainly Ireland, Scotland and points west. Swedes operated mainly in the Baltic and later in Russia.
But they were very mobile and vikings from different parts of Scandinavia operated in all theaters of the Viking expansion.
At that time, Danish, Swedish and Norweigan were so close that they were practically just dialects of Old Norse the common language.
Even Anglo-Saxon (aka Old English)was very close to Old Norse.