"a drain of brickwork or masonry under a road, railroad, etc.," 1773, origin unknown; OED calls it "A recent word of obscure origin." Perhaps, as Weekley suggested long ago, it is the name of a long-forgotten engineer or bridge-builder.
Originally architectural in English; transferred by early 15c. to anything having a curved form (eyebrows, feet, etc.). The commemorative or monumental arch is attested in English from late 14c. Compare Middle English Seinte Marie Chirche of the Arches (c. 1300) in London, later known as St. Mary-le-Bow, site of an ecclesiastical court, so called for the arches that supported its steeple (the modern church is by Sir Christopher Wren, rebuilt after the Great Fire of 1666).
ancient district of Anatolia on the southern coast of the Black Sea, from Latinized form of Greek Pontos "the Black Sea and the regions around it," literally "the sea," from a variant of the PIE root *pent- "to tread, go" that also produced Latin pons (genitive pontis) "bridge, passage;" see find (v.).
by 1914 as "to subject to psychoanalysis," short for psychoanalyze. From 1934 as "to outsmart" (also psych out), and by 1952 in bridge as "make a bid meant to deceive an opponent." From 1963 as "to unnerve." However to psych (oneself) up is from 1972; to be psyched up "stimulate (oneself), prepare mentally for a special effort" is attested from 1968.
[one kept in service] 1530s, "dependent or follower of a person of rank or position," agent noun from retain (v.). Also used in the general sense of "one who or that which retains or holds" (1540s). Meaning "dental structure used to hold a bridge in place" is recorded from 1887.