Word Origin & History
aghastmid-13c., agast, "terrified," pp. of M.E. agasten "to frighten," from a- intensive prefix + O.E. gæstan "to terrify," from gæst "spirit, ghost," The -gh- spelling appeared early 15c. in Scottish and is possibly a Flemish influence, or after ghost, etc. It became general after 1700.