There is a sheep-counting system in northern England, also used for counting stitches in knitting, which derives from a Brythonic Celtic language. Is there any surviving folklore that is known or reasonably hypothesised to derive from the culture of the Picts?
Ah, well look (here)[friendsofsabbath.org/Further_Research/British-Israel/Picts.pdf], it literally mentions it once...– blehJun 8, 2016 at 12:03
Actual folklore is stuff folk still say & do. It can be very hard to establish the origins of folkloric material. The linguistic connection is probably your best bet.
You might find this book interesting, though it is concerned with archaeology & history for the most part.
In Search of the Picts: A Celtic Dark Age Nation by Elizabeth Sutherland Trans-Atlantic Publications, 1994 ISBN 0094750106
The answer would appear to be no, there is no surviving folklore that is known or reasonably hypothesised to derive from the culture of the Picts. Apparently stone slabs from Pictish building projects is pretty much the only original material left from the Picts.
These carved stone slabs are the only record the Picts left of their history; the rest of their story is told by later Roman, Scottish, and English writers.
1Stone slabs don't count as folklore. Some historians claim that some Pictish folklore was adopted by the Celts, but I've not seen convincing arguments.– Chenmunka ♦Aug 29, 2022 at 16:27