fear (n.) Look up fear at Dictionary.com
Middle English fere, from Old English fær "calamity, sudden danger, peril, sudden attack," from Proto-Germanic *feraz "danger" (cognates: Old Saxon far "ambush," Old Norse far "harm, distress, deception," Dutch gevaar, German Gefahr "danger"), from PIE *per- "to try, risk," a form of verbal root *per- (3) "to lead, pass over" (cognates: Latin periculum "trial, risk, danger;" Greek peria "trial, attempt, experience," Old Irish aire "vigilance," Gothic ferja "watcher"); related to *per- (1) "forward, through" (see per).

Sense of "state of being afraid, uneasiness caused by possible danger" developed by late 12c. Meaning "feeling of dread and reverence for God" is from c.1400. To put the fear of God (into someone) is by 1905. Old English words for "fear" as we now use it were ege, fyrhto; as a verb, ondrædan.
fear (v.) Look up fear at Dictionary.com
Old English færan "to terrify, frighten," from a Proto-Germanic verbal form of the root of fear (n.). Cognates: Old Saxon faron "to lie in wait," Middle Dutch vaeren "to fear," Old High German faren "to plot against," Old Norse færa "to taunt."

Originally transitive in English; long obsolete in this sense but somewhat revived in digital gaming via "fear" spells, which matches the old sense "drive away by fear," attested early 15c. Meaning "feel fear" is late 14c. Related: Feared; fearing.