late 14c., "profound depth," from Old French golf "a gulf, whirlpool," from Italian golfo "a gulf, a bay," from Late Latin colfos, from Greek kolpos "bay, gulf of the sea," earlier "trough between waves, fold of a loose garment," originally "bosom," the common notion being "curved shape." This is from PIE *kuolp- "arch, curve, vault" (compare Old English hwealf"vault," a-hwielfan "to overwhelm," Old Norse holfinn "vaulted," Old High German welban "to vault").
Latin sinus underwent the same development, being used first for "bosom," later for "gulf" (and in Medieval Latin, "hollow curve or cavity in the body"). The geographic sense "large tract of water extending into the land" (larger than a bay, smaller than a sea, but the distinction is not exact and not always observed) is in English from c. 1400, replacing Old English sæ-earm. Figurative sense of "a wide interval" is from 1550s. The U.S. Gulf States so called from 1836. The Gulf Stream (1775) takes its name from the Gulf of Mexico.
mid-12c., "protect or defend from harm," from Old French covrir "to cover, protect, conceal, dissemble" (12c., Modern French couvrir), from Late Latin coperire, from Latin cooperire "to cover over, overwhelm, bury," from assimilated form of com-, here perhaps an intensive prefix (see com-), + operire "to close, cover," from PIE compound *op-wer-yo-, from *op- "over" (see epi-) + root *wer- (4) "to cover."
Sense of "to hide or screen" is from c. 1300, that of "to put something over (something else)" is from early 14c. Sense of "spread (something) over the entire extent of a surface" is from late 14c. Military sense of "aim at" is from 1680s; newspaper sense first recorded 1893; use in U.S. football dates from 1907. Betting sense "place a coin of equal value on another" is by 1857. Of a horse or other large male animal, as a euphemism for "copulate with" it dates from 1530s.
Meaning "to include, embrace, comprehend" is by 1868. Meaning "to pass or travel over, move through" is from 1818. Sense of "be equal to, be of the same extent or amount, compensate for" is by 1828. Sense of "take charge of in place of an absent colleague" is attested by 1970.
Middle English slēn, "strike, beat, strike so as to kill, commit murder," from Old English slean "to smite, strike, beat," also "to kill with a weapon, slaughter" (class VI strong verb; past tense sloh, slog, past participle slagen), from Proto-Germanic *slahanan "to hit" (source also of Old Norse and Old Frisian sla, Danish slaa, Middle Dutch slaen, Dutch slaan, Old High German slahan, German schlagen, Gothic slahan "to strike"). The Germanic words are said to be from PIE root *slak- "to strike" (source also of Middle Irish past participle slactha "struck," slacc "sword"), but, given certain phonetic difficulties and that the only cognates are Celtic, Boutkan says the evidences "point to a North European substratum word."
The verb slēn displays many nondialectal stem variants because of phonological changes and analogical influences both within its own paradigm and from other strong verbs. [Middle English Compendium]
Modern German cognate schlagen maintains the original sense of "to strike."
It is attested by late 12c. as "destroy, put an end to." The meaning "overwhelm with delight" (mid-14c.) preserves one of the wide range of meanings the word once had, including, in Old English, "stamp (coins); forge (weapons); throw, cast; pitch (a tent), to sting (of a snake); to dash, rush, come quickly; play (the harp); gain by conquest."
c. 1300, discoveren, "divulge, reveal, disclose, expose, lay open to view, betray (someone's secrets)," senses now obsolete, from stem of Old French descovrir "uncover, unroof, unveil, reveal, betray," from Medieval Latin discooperire, from Latin dis- "opposite of" (see dis-) + cooperire "to cover up, cover over, overwhelm, bury" (see cover (v.)).
At first with a sense of betrayal or malicious exposure (discoverer originally meant "informant"). Also in Middle English used in literal senses, such as "to remove" (one's hat, the roof from a building). The meaning "to obtain the first knowledge or sight of what was before not known," the main modern sense, is by 1550s.
Discover, Invent, agree in signifying to find out; but we discover what already exists, though to us unknown; we invent what did not before exist: as, to discover the applicability of steam to the purposes of locomotion, and to invent the machinery necessary to use steam for these ends. ... Some things are of so mixed a character that either word may be applied to them. [Century Dictionary]
Sense of "make famous or fashionable" is by 1908. Related: Discovered; discovering.
That man is not the discoverer of any art who first says the thing; but he who says it so long, and so loud, and so clearly, that he compels mankind to hear him—the man who is so deeply impressed with the importance of the discovery that he will take no denial, but at the risk of fortune and fame, pushes through all opposition, and is determined that what he thinks he has discovered shall not perish for want of a fair trial. [Sydney Smith, in Edinburgh Review, June 1826]