Phrasal verb from light (“to make bright, ignite”, verb) + up (“to a higher degree”, adverb).
Formed from light ‘to make bright, ignite’ + up ‘to a higher degree’
Proto-Indo-European *lewk- ‘to shine’
…
Proto-Germanic *leuhtą
Proto-West Germanic *leuht ‘light’
Old English lēoht
Middle English light ‘light, illumination’
English light
Proto-Germanic *upp ‘up’
Proto-West Germanic *upp
Old English upp
Middle English up ‘to a vertical axis’
English up
Today it means
verb To illuminate, to bring light to something, to brighten.
Language periods are conventional ranges, not dates for this word.
Etymograph / light up
Shirt and support for this word