eiderdown

[ahy-der-doun] /ˈaɪ dərˌdaʊn/
noun
1.
down, or soft feathers, from the breast of the female eider duck.
2.
a heavy quilt or comforter, especially one filled with eiderdown.
3.
a warm, lightweight knitted or woven fabric of wool, cotton, or man-made fibers, napped on one or both sides, used for sleepwear, infants' clothing, etc.
Origin
1765-75; eider + down2
British Dictionary definitions for eiderdown

eiderdown

/ˈaɪdəˌdaʊn/
noun
1.
the breast down of the female eider duck, with which it lines the nest, used for stuffing pillows, quilts, etc
2.
a thick warm cover for a bed, made of two layers of material enclosing a soft filling
3.
(US) a warm cotton fabric having a woollen nap
Word Origin and History for eiderdown
n.

1774; see eider + down (n.). Ultimately from Icelandic æðardun, via a Scandinavian source (cf. Danish ederdunn) or German Eiderdon.