"movable receptacle for detached papers or prints," 1722, porto folio; 1719 as port folio, from Italian portafoglio "a case for carrying loose papers," from porta, imperative of portare "to carry" (from PIE root *per- (2) "to lead, pass over") + foglio "sheet, leaf," from Latin folium (see folio). Usually something like a book cover with a flexible back, fastened with strings or clasps. Meaning "official documents of a state department" is from 1835, hence figuratively, of a minister of state. A minister without portfolio is one not in charge of a particular department. Meaning "collection of securities held" is from 1930; portfolio investment is from 1955.
late 14c., "set or kept apart, hidden, concealed," from French secret, adjective use of noun, from Latin secretum "a secret, a hidden thing" (see secret (n.)).
Secret agent is recorded by 1715; secret service is from 1737, "department of a government concerned with counterfeiting and other political and civil offenses done in secrecy;" secret police is by 1823. Secret weapon is by 1590s.
"the left side of a ship" (looking forward from the stern), 1540s, probably from the notion of "the side facing the harbor" (when a ship is docked); thus from port (n.1). On old-style vessels the steering oar was on the right side, thus they would tie up at a wharf on the other side. It replaced larboard in common usage to avoid confusion with starboard; officially so by Admiralty order of 1844 and U.S. Navy Department notice of 1846. As an adjective by 1857.
U. S. Navy Department, Washington, Feb. 18, 1846.
It having been repeatedly represented to the Department that confusion arises from the use of the words "larboard" and "starboard"' in consequence of their similarity of sound, the word "port" is hereafter to be substituted for "larboard." George Bancroft, Sec. of the Navy.
The whalemen are the only class of seamen who have not adopted the term port instead of larboard, except in working ship. The larboard boat was this boat to their great-grandfathers, and it is so with the present generation. More especially is this the case in the Atlantic and South Pacific fleets; but recently the term port-boat has come into use in the Arctic fleet. [Fisheries of U.S., V. ii. 243, 1887]
1859, "formation or development of cells by budding or division," from French prolifération, from prolifère "producing offspring," from Latin proles "offspring" (see prolific) + ferre "to bear, carry" (from PIE root *bher- (1) "to carry," also "to bear children"). The meaning "enlargement, extension, increase in number" is from 1920; especially of nuclear weapons by 1960 in the jargon of the U.S. State Department.