King Arthur's language was mixed with Latin, spoken by the Romans. Nervous is of Latin origin, from nervus, meaning a nerve, a rope-like structure. Uncertainty is of Latin origin, from certus, meaning a certificate. So un-certainty is an absence of a certificate, or a written document. Fear is of Old English origin, from faer, meaning danger.
Fear is related to the modern German gefahr, meaning danger.
Afraid is of Anglo-French origin, from afrayer, meaning frightened. Contro l is of Latin origin, from cribrum, a sieve. A sieve sifts materials, controlling their exit. Dying is of Old English or old German origin meaning to die. Terror is of Latin origin, from terrere, meaning filled with fear.