'pitch-black' originates from the word 'pitch,' which refers to a sticky, black substance used for waterproofing, combined with 'black' to emphasize complete darkness.

'pitch' changed from the Old English word 'pic,' which referred to a resinous substance, and eventually became part of the modern English expression 'pitch-black.'

Initially, 'pitch' referred to a substance, but over time, it evolved into a metaphor for complete darkness when combined with 'black.'