English
luminousness
From luminous + -ness.
Formed from luminous + -ness
Proto-Indo-European *lewk- ‘bright’
…
Proto-Italic *louksmən
Latin lūmen ‘light’
Latin lūminōsus ‘bright, luminous, full of light’
Middle French lumineus
English luminous
Today it means
noun The quality of being luminous.
Language periods are conventional ranges, not dates for this word.
Etymograph / luminousness