Five express fear, a feeling of uncertainty, uncertainty that's disagreeable or unpleasant. The ideas, the feelings, are expressed in words, English words, and English, like all language, is complex, related to it's history. The Normans, who spoke Old French, derived from Latin, were originally Northman who spoke a Scandinavian language, one related to German. 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.