So named because it met at Brooke House.
From The Private Palaces of London Past and Present by E. Beresford Chancellor (1908):
the “Brooke House Committee,” … had been appointed, in 1668, to examine into the expenditure of certain moneys granted by Parliament to Charles II. for the ostensible purpose of prosecuting the war with Holland, but which seem, as was not then unusual, to have been employed by his Majesty in more peaceful projects. We find Pepys, on December 18th, wending his way thither, and carrying with him by order, the “Contract-books, from the beginning to the end of the late war.” “I found him” (Colonel Thomson), says the Diarist, “finding of errors in a ship’s book, where he showed me many, which must end in the ruin, I doubt, of the Comptroller.”
“An Act for taking the Accompts of the several sums of money therein menconed,” 19 and 20 Car. II., c. I. The commissioners were empowered to call before them all Treasurers, Receivers, Paymasters, Principal Officers and Commissioners of the Navy and Ordnance respectively, Pursers, Mustermasters and Clerks of the Cheque, Accomptants, and all Officers and Keepers of his Majesties Stores and Provisions for Warr as well for Land as Sea, and all other persons whatsoever imployed in the management of the said Warr or requisite for the discovery of any frauds relating thereunto,” &c., &c. (“Statutes of the Realm,” vol. v., pp. 624,627).
This text comes from a footnote on a diary entry in the 1893 edition edited by Henry B. Wheatley.
Chart showing the number of references in each month of the diary’s entries.