'neck-and-neck' originates from English, specifically the word 'neck' (Old English 'hnecca'), where 'hnecca' meant 'the part of the body joining the head and shoulders.'

'neck-and-neck' developed from literal descriptions used in horse racing and other contests where two competitors' necks were level; the phrase 'neck and neck' came to be used figuratively for any very close contest.

Initially it described a literal physical position ('with necks side by side'); over time it evolved into the figurative meaning 'very closely matched' used in general contexts.