The Proto-Celtic word *onno
Word *onno
Meaning ash

Other words that might be of interest
*sūl- ‘sun’, *dumāko- ‘mist’, *dengwo ‘smoke, mist’, *mūko- ‘smoke’, *dwijat ‘smoke’, *taφnos- ‘fire’, *aidu ‘fire’, *angelo- ‘fire, light’, *loutwi ‘ashes’, *dubu ‘dark, black’, *skalī- ‘shadow’