I get the impression that a lot of pseudo-history portrays the Picts as being physically and culturally distinct from the other people of Northern Europe. For example, in Robert E. Howard's stories, they are descended from pre-Celtic groups with a lot of Neanderthal admixture (I think this was before it was generally accepted that most people have a bit of Neanderthal ancestry). More recently, I believe that some people have connected them with the Cro-Magnons (or Western European Hunter Gatherers, European Early Modern Humans, whatever they are called now... the dark-skinned, pre-Agricultural guys). There seems to have been a lot of talk about their language being a pre-Indo-European isolate or something too. Basically, they seem to be considered exceptional by a lot of people.

Where does this general trend come from? As far as I can tell, nobody at the time thought they were any more exotic than other barbarians. They seem to have basically just been another group of Britons. It's not entirely clear to me that anything distinguishes them from their neighbours except that the Romans called some of them 'Picts' and some of them other names. But by the early twentieth century it was apparently quite a popular idea and even today there is a vague air of weirdness about them.

Do we know when people started to get funny ideas about the Picts? Is it basically all REH's fault or did he draw on earlier sources? Are there any theories about the Picts which stand out as especially weird? Were they ever taken seriously by historians?

Also, while I'm asking about them, is there anything at all to indicate that the Picts engaged in body decoration any more than other Britons? Do we even know anything about their body painting? I believe that the idea they were tattooed is basically discredited now and they probably didn't make fancy patterns like we see in films, possibly didn't even use woad and were as likely to be green or turquoise as blue. Is there even good evidence that Britons actually painted themselves at all? It seems to all be based on a couple of vague mentions in some Roman accounts, mostly by people who never even went near the channel (although I think Julius Caesar does mention them being coloured and he would probably know).