cover-up (n.)

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.

Old English up, uppe, from Proto-Germanic *upp- "up" (source also of Old Frisian, Old Saxon up "up, upward," Old Norse upp; Danish, Dutch op; Old High German uf, German auf "up"; Gothic iup "up, upward," uf "on, upon, under;" Old High German oba, German ob "over, above, on, upon"), from PIE root *upo "under," also "up from under," hence also "over."

As a preposition, "to a higher place" from c. 1500; also "along, through" (1510s), "toward" (1590s). Often used elliptically for go up, come up, rise up, etc. Up the river "in jail" first recorded 1891, originally in reference to Sing Sing, which is up the Hudson from New York City. To drive someone up the wall (1951) is from the notion of the behavior of lunatics or caged animals. Insulting retort up yours (scil. ass) is attested by late 19c.