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.
If Mercury be afflicted in the sixth house, the native shall die in prison: if Saturn shall be in the twelfth, and Venus in the eighth, he shall end his days by precipitation. - William Lilly (1602.-1681.)