Etymology Dictionary

BAG,  a flexible case.  (E.)   M. E. bagge, P. Plowman, B. prol. 41; Ancren Riwle, p. 168.—O. Northumbrian Eng. met-bælig (Lindisfame MS.) or met-bælg, i.e. meat-bag (Rushworth MS.), a translation of Lat. pera, Luke, xvii. 35. + Goth. balgs, a wine-skin. + G. balg, a skin.   β. It is often considered as a Celtic word, but it is really a word common to the Celtic and Teutonic branches, and connecting the two.   Cf. Gaelic balg, sometimes bag, of which Macleod and Dewar say that it is 'a common Celtic vocable.'   γ. The M. E. form is doubtless due to the influence of Icel. baggi, a bag, formed from balgi by the assimilation so common in Icelandic.   The older form is clearly balg-, from the root appearing in bulge.   See Bulge.   Bag is a doublet of belly, q.v.; and the pl. bags is a doublet of bellows, q.v.   Der. bag, vb., bag-gy, bag-pipe (Chaucer, C. T. 567), bag-piper. [†]

ADDENDA

'Bulga, bælge oððe bylge'; Wright's Voc. ii. 12 (11th century).