Recent studies indicates that the name LUCCA comes from the word LEUK.
A very ancient word of Indo-European origin (Indo-European is supposed to be at the base of Indo-European languages including the living languages spread throughout the globe), LEUK means “light” and “shiny flat land”.
from: Lucca e il suo territorio. Toponomastica, dialettologia, critica linguistica
Autore Ambrosini Riccardo – 2006