1856, "private soldier in a regiment of the Line," from genitive of line (n.) + man (n.). Sports sense, in reference to umpires with specific duties in games with lines (originally tennis, also ice hockey) is from 1890.

late 14c., "resembling a line," from Old French lineal "pertaining to a line" (14c.), from Late Latin linealis "pertaining to a line," from linea "a string, line, thread" (see line (n.)). Compare linear. Related: Lineally.

also in-line, 1913 of printing, 1921 of engines, 1958 of computers, by 1989 of roller skates; from in + line (n.).

also roof-line, "the outline or silhouette of a roof or range of roofs," by 1829, from roof (n.) + line (n.).

also border-line, 1847, "strip of land along a frontier," from border (n.) + line (n.). As an adjective meaning "verging on" it is attested from 1903, originally in medical jargon.

1660s, "lines by which a figure is delineated," from out- + line (v.). Literally the outer or exterior line, but used freely for the principal or distinguishing lines. Meaning "rough draft in words" is from 1759.

1936, network of defensive fortifications built along the northern and eastern borders of France before World War II, in which the French placed unreasonable confidence, named for André Maginot (1877-1932), French Minister of War under several governments in the late 1920s and early 1930s. After the fall of France in 1940, for the next 40 years or so the phrase was associated with a mental attitude of obsessive reliance on defense.

in baseball, "a low batting average," (somewhere around .200) with the suggestion that any player hitting below it ought to feel a bit ashamed, by 1984, said to have been in humorous use in baseball clubhouses c. 1979, from the name of former Pirate, Mariner, and Ranger shortstop Mario Mendoza, who was noted for his defense but whose .215 lifetime batting average routinely left him at the bottom of weekly batting averages. The surname is Basque.

1883, "position in a line," from line (n.) + -age. From 1884 as a rough measure of printed material from the number of lines of text. Also "a payment or charge per line of print" (1888).

also water-line, 1620s, line where the water rises to on the hull of a ship afloat. As a makeup term for the inner rim of the eyelid, by 2011. From water (n.1) + line (n.).