late 14c., conservatyf, "tending to preserve or protect, preservative, having the power to keep whole or safe," from Middle French conservatif, from Medieval Latin conservativus, from Latin conservatus, past participle of conservare "to keep, preserve, keep intact, guard," from assimilated form of com-, here probably an intensive prefix (see com-), + servare "keep watch, maintain" (from PIE root *ser- (1) "to protect").
From 1840 in the general sense "disposed to retain and maintain what is established, opposed to innovation and change," or, in a negative sense "opposed to progress."
As a modern political tradition, "antagonistic to change in the institutions of a country," often especially "opposed to changes toward pure democracy," conservatism traces to Edmund Burke's opposition to the French Revolution (1790), but the word conservative is not found in his writing. It was coined by his French disciples (such as Chateaubriand, who titled his journal defending clerical and political restoration "Le Conservateur").
Conservative as the name of a British political faction first appeared in an 1830 issue of the "Quarterly Review," in an unsigned article sometimes attributed to John Wilson Croker. It replaced Tory (q.v.) by 1843, reflecting both a change from the pejorative name (in use for 150 years) and repudiation of some reactionary policies.
Strictly speaking, conservatism is not a political system, but rather a way of looking at the civil order. The conservative of Peru ... will differ greatly from those of Australia, for though they may share a preference for things established, the institutions and customs which they desire to preserve are not identical. [Russell Kirk (1918-1994)]
Phrases such as conservative estimate (1874), in which it means "characterized by caution, deliberately low," make no sense etymologically. Related: Conservatively; conservativeness.