also *es-, Proto-Indo-European root meaning "to burn, glow." 

It forms all or part of: ardent; ardor; area; arid; aridity; aril; arson; ash (n.1) "powdery remains of fire;" azalea; potash; potassium.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit asah "ashes, dust;" Hittite hat- "to dry up;" Greek azein "to dry up, parch," azaleos "dry;" Latin aridus "parched, dry," ārēre "to be dry," āra "altar, hearth;" Armenian azazem "I dry up;" Old English æsce "ash," Old High German asca, Gothic azgo "ashes." 

1530s, "vacant piece of ground," from Latin area "level ground, open space," used of building sites, playgrounds, threshing floors, etc.; which is of uncertain origin. Perhaps an irregular derivation from arere "to become dry" (see arid), on notion of "bare space cleared by burning." The generic sense of "any particular amount of surface (whether open or not) contained within any set of limits" is from 1560s. Area code in the North American telephone systems is attested from 1959.

"dryness, want of moisture," 1590s, from  French aridité or directly from Latin ariditatem (nominative ariditas) "dryness," from aridus "dry" (see arid). Figuratively from 1690s; the Latin word was used figuratively of unadorned styles as well as stingy men.

"accessory covering of seeds," 1783, from Modern Latin arillus, from Medieval Latin arilli, Spanish arillos "dried grapes, raisins," from Latin aridus "dry" (see arid).

also semiarid, "having rather more precipitation than what is arid," 1886, from semi- + arid.