'ghostly' originates from Old English, specifically the word 'gāstlic' (also recorded as 'gastlic'), where 'gāst/gast' meant 'spirit, breath' and the suffix '-lic' meant 'like' or 'having the nature of'.

'ghostly' changed from Old English 'gāstlic' to Middle English forms such as 'gostly'/'gostely', with the modern spelling 'ghostly' emerging later in Modern English.

Initially it meant 'like a spirit' or 'spiritual in nature'; over time it retained that sense while also developing related senses of 'pale' and 'eerie' in ordinary usage.