mock-up (n.)

mid-15c., mokken, "make fun of," also "to trick, delude, make a fool of; treat with scorn, treat derisively or contemptuously;" from Old French mocquer "deride, jeer," a word of unknown origin. Perhaps from Vulgar Latin *muccare "to blow the nose" (as a derisive gesture), from Latin mucus; or possibly from Middle Dutch mocken "to mumble" or Middle Low German mucken "grumble." Perhaps ultimately it is imitative of such speech. Related: Mocked; mocking. Replaced Old English bysmerian. The sense of "imitate, simulate, resemble closely" (1590s, as in mockingbird ; also see mock (adj.)) is from the notion of derisive imitation.

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.