pigments such as basic copper carbonate. Tattooing is understood to have been practised by the Caledonians at the time of the campaign of Septimius Severus in 208 AD, as reported by Herodian, and Isidore of Seville reports in the early 7th century that the practice was continued by the Picts. While this seems logical as an origin for the word Picts, an alternative suggestion is that the Latin Picti was derived from a native form, perhaps related etymologically to the Gallic Pictones. The Picts were called Cruithni in Old Irish and Prydyn in Old Welsh. These are lexical cognates, from the proto-Celtic *kwritu 'form', from which *Pretania (Britain) also derives. Pretani (and with it Cruithni and Prydyn) is likely to have originated as a generalised term for any native inhabitant of Britain. This is similar to the situation with the Gaelic name of Scotland, Alba, which originally seems to have been a generalised term for Britain. It has been proposed that the Picts may have called themselves Albidosi, a name found in the Chronicle of the Kings of Alba during the reign of Máel Coluim mac Domnaill. History A Pictish confederation was formed in Late Antiquity from a number of tribes, but how and why are not known. Some scholars have speculated that it was partly in response to the growth of the Roman Empire. The Pictish Chronicle, the Anglo-Saxon Chronicle and the early historiographers such as Bede, Geoffrey of Monmouth, Holinshed, etc. all present the Picts as conquerors of Alba from Scythia. However, no credence is now given to that view. Pictland had previously been described by Roman writers and geographers as the home of the Caledonii. These Romans also used other names to refer to tribes living in that area, including Verturiones, Taexali and Venicones. But they may have heard these other names only second- or third-hand, from speakers of Brittonic or Gaulish languages, who may have used different names for the same group or groups. Pictish recorded history begins with the Roman invasion of Britain and the efforts of the Picts to resist Roman attempts to control the part of the island referred to as Caledonia. There is considerable conflict of opinion over the level of success that should be accorded to the invasion of Caledonia and opinion appears sharply divided between older accounts and those of modern writers according to their political views over Scottish sovereignty.