Library

applied, e.g. to the shop or warehouse of a bookseller. In various applications more or less specific. a. Applied to a room in a house, etc.; also, a bookcase. In mod. use, the designation of one of the set of rooms ordinarily belonging to an English house above a certain level of size and pretension.

c1374 CHAUCER Boeth. I. pr. v. 15 (Camb. MS.) The walles of thi lybrarye aparayled and wrowht with yuory and with glas.
1430-40 LYDG. Bochas VI. i. (1554) 142 Bochas pensief stode in his library.
1488 Inventory in Archæologia XLV. 120 On the south side of the Vestrarie standeth a grete library.
1779 M. TYSON in Lett. Lit. Men (Camden) 195, I there saw his library, i.e. the Room which once contained his Books.
1794 MRS. RADCLIFFE Myst. Udolpho i, The library occupied the west side of the chateau.
1854 W. COLLINS Hide & Seek II. ii. (1861) 161 Zack descended cautiously to the back parlour, which was called a ‘library’.

pasted from OED, 2nd Edition