An Etymological Dictionary of the German Language/Flaum
Flaum, m. (Up.G. Pflaum also), ‘down,’ from MidHG. phlûme, f., OHG. pflûma, ‘down,’ from Lat. plûma, whence also AS. plûmfëþere. As the shifting of the initial sound proves, however, the word must have been borrowed in the earlier OHG. period; comp. the OIr. word (also derived from the Lat.) clúm, ‘feather’ (OW. plumauc, ‘pillow’). Scand. and E. have for Flaum an apparently genuine Teut. word (see Daune. It is certainly recorded by Pliny that Teut. tribes in the olden time sent flocks of geese to Rome; but perhaps it was only ‘down’ (see also Flocke), which was valuable to the Southerners, and so the Lat. pluma may hare been introduced into Teut. at an early period. The initial f of the ModHG. form for pf may be due to the connection with Feder.