'well-perfused' is a modern English compound combining the adverb 'well' and the past participle 'perfused' (from Latin 'perfundere'), where 'well' meant 'in a good or sufficient manner' and Latin 'per-' meant 'through' while 'fundere' meant 'to pour'.

'perfused' derives from Latin 'perfundere' ('per-' + 'fundere') and passed into Late Latin/Old French forms before entering Middle English as forms related to 'perfuse' and later becoming the modern English 'perfuse' and its past participle 'perfused'; 'well-perfused' is a straightforward modern formation using 'well' + past participle.

Originally 'perfundere' meant 'to pour through' or 'to pour over'; over time English 'perfuse' came to mean 'to cause to flow through or over (a structure), especially with fluid such as blood', and 'well-perfused' now specifically describes tissue or an organ with good blood flow.