Metroliner (n.)

mid-14c., "bishop having general superintendency over other bishops of his province," from Late Latin metropolitanus, from Greek metropolis "mother city" (from which others have been colonized), parent state of a colony," also "capital city," and, in Ecclesiastical Greek, "see of a metropolitan bishop," from meter "mother" (see mother (n.1)) + polis "city" (see polis).

In the early church, the bishop of a municipal capital of a province or eparchy, who had general superintendence over the bishops in his province. In modern Catholic use, an archbishop who has bishops under his authority; in the Greek church still the bishop of a municipal capital of a province, ranking above an archbishop.

"vessel belonging to a shipping line," 1838, from line (n.) on the notion of a succession of ships plying between ports along regular "lines," as distinguished from transient ships using those ports. (Line in this sense is attested by 1786 in reference to stagecoaches.) Earlier it meant "man of war, ship of the line" (1829).

The cosmetic sense is by 1904, originally of actor's makeup where it might be used to draw wrinkles, as well as outline the eyes or lips. The type of baseball hit (forcible and parallel to the ground) was so called from 1874 (line drive is attested from 1899).