Etymology
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obstruct (v.)

1610s, "to block or stop up with obstacles or impediments," a back-formation from obstruction or else from Latin obstructus, past participle of obstruere "build up, block, block up, build against, stop, bar, hinder," from ob "in front of, in the way of" (see ob-) + struere "to pile, build" (from PIE *streu-, extended form of root *stere- "to spread"). Figurative sense of "to hinder, impede, retard, delay" (justice, the law, etc.) is by 1640s. Related: Obstructed; obstructing.

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Rhode Island 

U.S. state, the region is traditionally said to have been named by Italian explorer Giovanni da Verrazzano when he passed through in 1524, based on an imagined similarity between modern Block Island and the Greek Isle of Rhodes. More likely it is from Roodt Eylandt, the name Dutch explorer Adriaen Block gave to Block Island c. 1614, literally "red island," so called for the color of its cliffs. Under this theory, the name was altered by 17c. English settlers by folk-etymology influence of the Greek island name (see Rhodes) and then extended to the mainland part of the colony. By 1685 the island had been renamed for Block. The Rhode Island red domestic fowl was so called by 1896, for its plumage.

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mask (v.)

1560s, "to take part in a masquerade" (a sense now obsolete); 1580s as "to wear a mask," also "disguise (feelings, etc.) under an assumed outward show;" from mask (n.) and French masquer. Military sense of "conceal" (a battery, etc.) from the view of the enemy" is from 1706. Related: Masked; masking. Masking tape recorded from 1927; so called because it is used to block out certain surfaces before painting.

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blocking (n.)
1630s, verbal noun from present participle of block (v.2). By 1891 in U.S. football; by 1961 in theater.
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sunscreen (n.)
1738 as an object to block the sun's rays, from sun (n.) + screen (n.). As a type of lotion applied to the skin, by 1954.
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blocker (n.)
c. 1400 of a tool, c. 1600 of a person, agent noun from block (v.1). U.S. football sense from 1914.
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monolithic (adj.)

1802, "formed of a single block of stone;" 1849, "of or pertaining to a monolith," from monolith + -ic. Figurative use from 1920. Related: Monolithal (1813).

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roadblock (n.)

"barrier or obstruction on a road," usually for military or police purposes, 1940, from road (n.) + block (n.2).

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blockhouse (n.)
"detached fort blocking a landing, mountain pass, etc., 1510s, of uncertain origin; perhaps from Middle Dutch blokhuis, German Blockhaus, French blockhaus (from one of the German words), all from 16c.; see block (v.1). Later "building with an overhanging upper story with loopholes for firing through" (often a square of logs serving as a fort in rough country), which seems to connect to block (n.1). For second element, see house (n.).
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up (v.)

1550s, "to drive and catch (swans)," from up (adv.). Intransitive meaning "get up, rise to one's feet" (as in up and leave) is recorded from 1640s. Sense of "to move upward" is recorded from 1737. Meaning "increase" (as in up the price of oil) is attested from 1915. Compare Old English verb uppian "to rise up, swell." Related: Upped; upping. Upping block, used for mounting or dismounting horses, carriages, etc., is attested from 1796 (earlier was horsing-block, 1660s).

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