1853, "unselfishness, devotion to the welfare of others, the opposite of egoism," from French altruisme, coined or popularized 1830 by French philosopher Auguste Comte, with -ism + autrui (Old French altrui) "of or to others," from Latin alteri, dative of alter "other" (see alter). The -l- in the French coinage perhaps is an etymological reinsertion from the Latin word.
If we define altruism as being all action which, in the normal course of things, benefits others instead of benefiting self, then, from the dawn of life, altruism has been no less essential than egoism. Though primarily it is dependent on egoism, yet secondarily egoism is dependent on it. [Herbert Spencer, "The Data of Ethics," 1879]
There is a fable that when the badger had been stung all over by bees, a bear consoled him by a rhapsodic account of how he himself had just breakfasted on their honey. The badger replied peevishly, "The stings are in my flesh, and the sweetness is on your muzzle." The bear, it is said, was surprised at the badger's want of altruism. ["George Eliot," "Theophrastus Such," 1879]
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."