'breakneck' originates from Middle English, specifically the words 'breken' meaning 'to break' and 'nekke' meaning 'neck'.

'breken' and 'nekke' combined to form the term 'breakneck', which has been used in English since the 16th century to describe something extremely fast or dangerous.

Initially, it meant 'to break one's neck', but over time it evolved into its current meaning of 'dangerously fast'.