allergy n.

Proto-Indo-European root meaning "beyond."

It forms all or part of: adulteration; adultery; alias; alibi; alien; alienate; alienation; allegory; allele;  allergy; allo-; allopathy; allotropy; Alsace; alter; altercation; alternate; alternative; altruism; eldritch; else; hidalgo; inter alia; other; outrage; outrageous; outre; parallax; parallel; subaltern; synallagmatic; ulterior; ultimate; ultra-.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit anya "other, different," arana- "foreign;" Avestan anya-, Armenian ail "another;" Greek allos "other, different, strange;" Latin alius "another, other, different," alter "the other (of two)," ultra "beyond, on the other side;" Gothic aljis "other," Old English elles "otherwise, else," German ander "other."

Proto-Indo-European root meaning "to do."

It forms all or part of: allergic; allergy; argon; boulevard; bulwark; cholinergic; demiurge; dramaturge; energy; erg (n.1) "unit of energy;" ergative; ergonomics; ergophobia; George; georgic; handiwork; irk; lethargic; lethargy; liturgy; metallurgy; organ; organelle; organic; organism; organize; orgy; surgeon; surgery; synergism; synergy; thaumaturge; work; wright; wrought; zymurgy.

It is the hypothetical source of/evidence for its existence is provided by: Greek ergon "work," orgia "religious performances;" Armenian gorc "work;" Avestan vareza "work, activity;" Gothic waurkjan, Old English wyrcan "to work," Old English weorc "deed, action, something done;" Old Norse yrka "work, take effect."