bruxism

The story

1. Ancient Greek · derived fromβρύκω“bite, chew; devour, gobble; grind one's teeth, gnash”
2. Ancient Greek · derived fromβρυχή“grinding of teeth”
3. English todaybruxism

From Ancient Greek βρυχή (brukhḗ, “grinding of teeth”) + English -ism (suffix forming nouns indicating a tendency of action, behaviour, condition, or state). The word βρυχή is derived from Ancient Greek βρύκω (brúkō, “bite, chew; devour, gobble; grind one's teeth, gnash”). Note that the stem brux- is an irregular transliteration from Ancient Greek (the form brychism would be expected).