'blood-pressure-lowering' is a Modern English compound formed from 'blood', 'pressure', and the present participle 'lowering'. Here 'blood' referred to the bodily fluid, 'pressure' to force or tension (in this sense, arterial tension), and 'lowering' is the present participle of 'lower' meaning 'to make less'.

'blood' comes from Old English 'blōd'; 'pressure' derives from Latin root 'premere' via Old French (e.g. 'pression') and Middle English forms to modern 'pressure'; 'lower' developed through Middle English from older Germanic verbs meaning 'to make low', and the suffix '-ing' forms the present participle. These elements were compounded in Modern English to describe an action or property that reduces blood pressure.

Initially the separate parts had literal meanings related to bodily fluid ('blood') and force ('pressure'); combined with 'lowering' the compound came to mean 'causing a reduction in arterial blood pressure', a specialized medical/pharmaceutical sense.