'asphodel' originates from Greek, specifically the word 'asphodelos' (ἀσφόδελος), which was used in ancient Greek to name the plant.

'asphodel' passed into Latin as 'asphodelus', then into Old French (e.g. 'asfodel'), and entered Middle English before becoming the modern English 'asphodel'.

Initially it referred to the particular plant named in Greek poetry; over time it retained its botanical sense while also acquiring a strong literary/poetic association with the afterlife and the plains of the dead.