Luminal (n.) Look up Luminal at
trade name of phenobarbitone, used as a sedative and hypnotic, coined 1912 in German from Latin lumen "light," related to lucere "to shine" (see light (n.)), + -al (3), "the root here being used, very irregularly, as an equivalent of pheno- [Flood].
luminal (adj.) Look up luminal at
"of or pertaining to a lumen," 1897, with -al (1).