ghastly: [14] Despite its similarity in form and sense, ghastly is not related to ghost. It was formed from the Middle English verb gasten ‘terrify’, which may have been a descendant of the Old English verb gǣstan ‘torment’ (source of aghast). The spelling with gh-, based on ghost, was first used by the 16th-century poet Edmund Spenser, and in due course caught on generally. => aghast[ghastly etymology, ghastly origin, 英语词源]