Correct spelling for the English word "frightning" is [fɹˈa͡ɪtənɪŋ], [fɹˈaɪtənɪŋ], [f_ɹ_ˈaɪ_t_ə_n_ɪ_ŋ] (IPA phonetic alphabet).
The word "frightening" is derived from the verb "frighten", which can be traced back to Middle English. It ultimately comes from the Old English word "fȳrhtan", which means "to frighten" or "to terrify". "Fȳrhtan" is related to the Old High German word "forhtōn", meaning "to fear" or "to be afraid". Both of these words, in turn, are believed to have originated from the Proto-Germanic root "furchtōną", meaning "to fear" or "to be afraid".