'bloodshot' is a compound of the noun 'blood' and the adjective/participle 'shot' (from 'to shoot' or earlier senses meaning 'marked or streaked'), formed in English to describe something marked with blood or bloodlike streaks.

'blood' originates in Old English 'blōd' meaning 'blood', and 'shot' in this compound comes from older forms related to past participle/adjective 'shot' (Middle English usage meaning 'marked or spotted'); together they formed 'bloodshot' in Early Modern English to describe reddened eyes.

Initially used broadly to mean 'marked or spotted with blood', the term became specialized to describe eyes that are reddened or injected with blood and now primarily refers to that condition.