"one engaged in the business of buying commercial commodities and selling them again for profit," early 13c., marchaunt (late 12c. as a surname), from Anglo-French marchaunt "merchant, shopkeeper" (Old French marcheant, Modern French marchand), from Vulgar Latin *mercatantem (nominative *mercatans) "a buyer," present participle of *mercatare, frequentative of Latin mercari "to trade, traffic, deal in" (see market (n.)). Meaning "fellow, chap" is from 1540s; with a specific qualifier, and suggesting someone who deals in it (such as speed merchant "one who enjoys fast driving," by 1914).
"relating to trade or commerce; pertaining to merchants," c. 1400, from merchant (n.) and from Old French marcheant (adj.).
late 14c., "seacoast;" see marine (adj.). Meaning "collective shipping of a country" is from 1660s. Meaning "soldier who serves on a ship" is from 1670s, a separate borrowing from French marine, from the French adjective. Phrase tell that to the marines (1805) originally was the first half of a retort expressing disbelief in some statement made or story told:
"Upon my soul, sir," answered the lieutenant, "when I thought she scorned my passion, I wept like a child."
"Belay there!" cried the captain; "you may tell that to the marines, but I'll be d----d if the sailors will believe it." ["John Moore," "The Post-Captain; or, the Wooden Walls Well Manned," 1805]
The book, a rollicking sea romance/adventure novel, was popular in its day and the remark is a recurring punch line in it (repeated at least four times). It was written by naval veteran John Davis (1774-1854) but published under the pseudonym "John Moore." Walsh records that, among sailors, marines are "a proverbially gullible lot, capable of swallowing any yarn, in size varying from a yawl-boat to a full-rigged frigate."
mid-15c., "found in or pertaining to the sea," from Old French marin "of the sea, maritime," and directly from Latin marinus "of the sea," from mare "sea, the sea, seawater," from PIE root *mori- "body of water." The Old English word was sælic.
1824, "one of an imaginary corps of mounted sailors," hence "a person out of his element and unfit for his place" [Century Dictionary], from horse (n.) + marine (n.). However by 1878 the term was being used in fact in reference to cavalrymen pressed into marine service or seamen mounted as an improvised shore defense.
1800, "marine shop," from junk (n.1) in the sense "discarded articles from ships." By 1951 in the non-marine sense "junk-dealer."
also A1, A-one, "first-rate," 1837 (in Dickens); a figurative use from Lloyd's of London marine insurance company's system for selective rating of merchant vessels ("Register of British and Foreign Shipping"), where it is the designation for ships in first-class condition. The letter refers to the condition of the hull of the ship itself, and the number rating to the equipment. Also used in equivalent ratings in U.S., where colloquially it is sometimes expanded to A No. 1 (which is attested by 1848 as top rating of entries in an agricultural fair).
