From OE 'gāst' (spirit, breath) — originally 'soul' (as in Holy Ghost); the 'gh' spelling was introduced by printer William Caxton.
An apparition of a dead person; a faint trace or possibility of something; the soul or spirit.
From Old English 'gāst' (spirit, soul, breath, life), from Proto-Germanic *gaistaz (spirit, ghost), from PIE *ǵheysd- (anger, agitation) or *ǵheys- (to be excited, to be frightened). The original meaning was 'spirit' or 'soul' — the 'Holy Ghost' preserves this older sense. The modern meaning 'specter of a dead person' developed during the Middle English period. The spelling with 'gh' was introduced by William Caxton, influenced by Flemish 'gheest.' Key roots: *gaistaz (Proto-Germanic: "spirit, ghost"), *ǵheysd- (Proto-Indo-European: "anger
The 'gh' in 'ghost' is William Caxton's fault. The first English printer (1470s) was heavily influenced by Flemish spelling — in Dutch, the word is 'geest' (gheest). Caxton added the 'h' to the English word, which had been spelled 'gost' or 'gast' for six centuries. We have been pronouncing it wrong ever since — the 'gh' was never meant to be silent; it was a printing import that stuck.