Emily Dickinson Lexicon

BLAD'DER, n. [Sax. blædr, blædra, bleddra, a bladder, and blæd, a puff of wind, also a goblet, fruit, the branch of a tree; W. pledren, a bladder; Sw. and Dan. blad, a page, a leaf, Eng. a blade; D. blad, a leaf, page, sheet, a board, a blade, a plate; G. blatt, a leaf; blatter, a blister, which is our bladder. The Germans express bladder by blase, D. blaas, which is our blaze. Hence we observe that the sense is taken from swelling, extending, dilating, blowing; Sax. blawan, to blow; W. blot or blwth, a puff or blast; W. pled, extension, from llêd, breadth; L. latus.]

1. A thin membranous bag in animals, which serves as the receptacle of some secreted fluid; as, the urinary bladder, the gall bladder, &c. By way of eminence, the word, in common language, denotes the urinary bladder, either within the animal, or when taken out and inflated with air. – Encyc. Johnson.
2. Any vesicle, blister or pustule, especially if filled with air, or a thin, watery liquor.
3. In botany, a distended membranaceous pericarp. – Martyn.