Picts- a celtic tribe

The Picts inhabited Pictavia or Pictland - Caledonia (Scotland), north of the River Forth - prior to the invasion of the Scotti (Sgaothaich) from Ireland. The name Pict first appears in a panegyric written by Eumenius in 297 AD. Although Picti is usually assumed to mean painted or tattooed (as in Latin) it may have a Celtic origin. The Goidelic Celts called the Picts Cruithne and the Brythonic Celts knew them as prydyn, whence Britain. History …

…Wars on the tribes from the areas where Picts (later) lived, states that they have "designs carved into their faces by iron". If they used woad, then it probably penetrated under the skin as a tattoo. More likely, the Celts used copper for blue tattoos (they had plenty of it) and soot-ash carbon for black. Further study of bog bodies may provide more information on the specific tattooing techniques (if any) used by the Picts.