Paris underground, 1904, from French abbreviation of Chemin de Fer Métropolitain "Metropolitan Railway" (see metropolitan (adj.)). French chemin de fer "railroad" is literally "iron road." Construction began in 1898.
early 15c., "fixed standard of measure" (surname Gageman is early 14c.), from Old North French gauge "gauging rod" (see gauge (v.)). Meaning "instrument for measuring" is from 1670s; meaning "distance between rails on a railway" is from 1841.
Railway-gage, the distance between perpendiculars on the insides of the heads of the two rails of a track. Standard gage is 4 feet 8 1/2 inches; anything less than this is narrow gage; anything broader is broad gage. The dimension was fixed for the United States by the wheels of the British locomotive imported from the Stephenson Works in 1829. [Century Dictionary]
also cloakroom, 1827, "a room connected with an assembly-hall, opera-house, etc., where cloaks and other articles are temporarily deposited," from cloak (n.) + room (n.). Later extended to railway offices for temporary storage of luggage, and by mid-20c. sometimes a euphemism for "bathroom, lavatory."
1815, "one who dines," agent noun from dine. Meaning "railway car for eating" is 1890, American English; of restaurants built to resemble dining cars (or in some cases actual converted dining cars) from 1935. The Diner's Club credit card system dates from 1952.