Term: thulium (Tm)
Literally meaning: “pertaining to Thoule land”
According Greek explorer Pytheas of Massalia (4 t6h cen BC) Thoule was the northernmost habitable region of the world. Pytheas about 330 BC was travelled to England and then to Thule where the night was very short (2-3 hours) and its north sea solid.
The name of element was given after Thule, the region in the far north as Scandinavia land where the element had been found.
Thulium was found by Swedish chemist Per Teodor Cleve in 1879 while trying to purify erbia (Er2O3) from known impurities. He obtained finally two substances; one brown (oxide of element holmium) and one green (oxide of element thulium).
Thulium is a chemical element with atomic number 69 and atomic mass 168.93421. It is used in portable X-ray devices, in alloys with other rare metals and in solid-state lasers.