aghast [LME] Gast (originally gaestan) was an Old English word meaning ‘frighten or terrify’. It was still being used in this sense in Shakespeare’s day: ‘Or whether gasted by the noise I made, Full suddenly he fled’ (King Lear). This gave rise to agast, which had the same meaning. The spelling aghast (probably influenced by the spelling of *ghost) was originally Scottish but became generally used after 1700. Ghastly [ME] comes from the same word. The sense ‘objectionable’ dates from the mid 19th century.