The inhabitants of Scotland in ancient times were known to their neighbors as the Picts. Nobody is sure where this word comes from, and it may from the Latin for "painted" (presumably because they covered themselves with tattoos). From Pictish words that survive in place names and the like, we have figured out that their language was Celtic and closely related to Welsh.
The Picts left behind, among other monuments, a bunch of stones carved with symbols. The nature of these symbols has long been debated, and it has been suggested that they might represent a written language. Now a statistical study of the symbols provides some evidence that they are writing, that is, the study showed that the number, frequency, and ordering of the symbols is similar to what you get in a symbolic language. This is very interesting, but it doesn't really get us any closer to deciphering what the symbols might mean.
Above, one of the most famous stones; below, part of the symbol vocabulary.