It’s a long way ’round, but the name of the plant known as the Daffodil and its flower were originally and properly still should be asphodel, though the later name denotes a kind of narcissus rather than a true asphodel.
In the fifteenth century, perhaps at first in imitation of some king or prince who lisped, folks began to change asphodel to affodill.
Then in the sixteenth century, perhaps to give the word a Frenchified aspect (such as in altering Albert to D’Albert), the name suddenly gained a new initial, and daffodil was born.
The names daffodilly and daffodowndilly are merely poetic substitutions, used as early as the sixteenth century, even by so renowned a poet as Edmund Spenser.