acclivity (n.)

"upward slope of ground," 1610s, from Latin acclivitatem (nominative acclivitas) "an ascending direction, rising grade, upward steepness," from acclivis "mounting upwards, ascending," from ad "to, up to" (see ad-) + clivus "hill, a slope," from PIE *klei-wo-, suffixed form of root *klei- "to lean."