Meaning

originBorrowed from Scots lum, Early Scots lumb; further etymology uncertain, but probably from Cumbric *lümon, related to Welsh llumon (“chimney”) (obsolete), from Proto-Celtic *loimono. Possibly at least influenced by Old French lum (“light”), lume (“cooking fire”) (compare French lumière (“light; cavity or channel within a tube or tubular organ, lumen; opening”)), from Latin lūmen (“light; light…

Etymology from Wiktionary, CC BY-SA 3.0