1868, from bi- "two" + a Latinized form of Greek kyklos "circle, wheel" (see cycle (n.)), on the pattern of tricycle; both the word and the vehicle superseding earlier velocipede.
The English word is said in some dictionaries to be probably not from French, but the 1868 citations are in a French context: The velocipedes, about which the Parisians have run mad at the present moment, are of various kinds. ... The two wheel velocipedes, the bicycles as they are styled, are intended for the male sex only, and are by far the swiftest machines. ["Supplement to the Courant," Hartford, Conn., Dec. 16, 1868]. Pierre Lallement, employee of a French carriage works, improved Macmillan's 1839 pedal velocipede in 1865 and took the invention to America. See also pennyfarthing. As a verb, from 1869.
The velocipede of 1869 was worked by treadles operating cranks on the axle oi the front wheel. This was modified in the earliest form of the bicycle by greatly increasing the relative size of the driving-wheel and bringing the rider directly over it. Later the "safety" bicycle was introduced, in which the wheels were made of equal or nearly equal size, and for the direct action upon the front wheel was substituted indirect action upon the rear wheel, by means of a chain and sprocket-wheels .... [Century Dictionary]