It is the origin of many English words related to sleep, such as:
* Somnolent: Sleepy or drowsy
* Insomnia: Difficulty sleeping
* Somnambulism: Sleepwalking
* Hypnos: The Greek god of sleep, closely related to Somnus
It's interesting to note that "somnus" is also the name of the Roman god of sleep, who was often depicted as a winged youth.