1510s, "to walk at a steady rate," from pace (n.). Meaning "to measure by pacing" is from 1570s. That of "to set the pace for" (another) is from 1886. Related: Paced; pacing.

also pace-maker, 1884, "one who sets the pace for others," originally a rider or boat that sets the pace for others in training. Meaning "the node of the heart which determines the beat rate" is from 1910; sense of "man-made device for stimulating and regulating heartbeat" (short for artificial pacemaker) is from 1951. From pace (n.) + maker.

1660s, "a horse whose natural gait is a pace," agent noun from pace (v.). As "one who measures by pacing," by 1835.

word-forming element in science meaning "thick, large, massive," from Latinized form of Greek pakhys "thick, fat, well-fed, dense, stout,"  from PIE *bhengh- "thick, fat" (source also of Sanskrit bahu- "much, numerous;" Avestan bazah- "height, depth;" Armenian bazum "much;" Hittite pankush "large," panku- (adj.) "total;" Old Norse bingr "heap," Old High German bungo "a bulb;" Latvian biezs "thick").

1953, from Japanese, "pinball machine," also "slingshot, handgun," from pachin, of echoic origin, + diminutive suffix -ko.

in zoology, "thick-headed," by 1862, from pachy- "thick, large" + -cephalic. Related: Pachycephalous (1890).

1838, from French pachyderme (c. 1600), adopted as a biological term for non-ruminant hoofed quadrupeds 1797 by French naturalist Georges Léopole Chrétien Frédéric Dagobert, Baron Cuvier (1769-1832), from Greek pakhydermos "thick-skinned," from pakhys "thick, large, massive" (see pachy-) + derma "skin" (from PIE root *der- "to split, flay, peel," with derivatives referring to skin and leather). Cuvier's order of Pachydermata is now disused in zoology, but pachyderm remains in common use to describe elephants, rhinoceroses, hippopotamuses, etc. Related: Pachydermal; pachydermic; pachydermatous.

genus of small, evergreen plants, 1813, from Modern Latin (Andre Michaux, 1803), from Greek pakhys "thick" (see pachy-) + anēr (genitive andros) "man" (from PIE root *ner- (2) "man"), which is used in botany to mean "stamen, having stamens" (the plant is notable for its four stamens).

"policy or doctrine of rejecting war and violence in solving disputes," especially in international affairs, 1902, from French pacifisme (1901), which was apparently coined by French anti-war writer Émile Arnaud (1864-1921), from pacifique (see pacific). Also compare pacificism.

1540s, "tending to make peace, concillatory," from French pacifique, from Latin pacificus "peaceful, peace-making," from pax (genitive pacis) "peace" (see peace) + combining form of facere "to make" (from PIE root *dhe- "to set, put"). Meaning "peaceful, characterized by peace or calm" is recorded from 1630s. Related: Pacifical (mid-15c., "of a peaceful nature"); pacifically.

Pacific, making or desiring to make peace; peaceable, desiring to be at peace, free from the disposition to quarrel; peaceful, in a state of peace. [Century Dictionary, 1895]

The Pacific Ocean (1660 in English) was famously so called in 1519 by Magellan when he sailed into it and found it calmer than the stormy Atlantic, or at least calmer than he expected it to be. According to an original account of the voyage by an Italian named Pigafetta, who was among the adventurers, Magellan gave the entrance to what Pigafetta calls "the South Sea" the Latin name Mare Pacificum.  The U.S. Pacific Northwest is so called by 1889.