7 letters · 11 points in Scrabble
noun a metallic element of the rare earth group; used in lasers; occurs in apatite and monazite and xenotime and ytterbite
originFrom Ytterby + -ium, named after Ytterby, Sweden, the same etymological source as yttrium, erbium, and ytterbium.
Etymology from Wiktionary, CC BY-SA 3.0