Lucas shares its root with the Latin lux, light, and the name is often read as describing illumination in a literal sense -- clarity brought into a space rather than metaphorical enlightenment alone. It suggests someone whose presence tends to make things easier to see, plainly rather than dramatically.
The comets should be used when they appear and in what they rule; just as fixed stars, they have to be used according to each one's nature. - Picatrix (Andalusia, ~1000.AD)