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]
1785, in metaphysics, "the theory that a person has no proof that anything exists outside his own mind," from French égoisme (1755), from Modern Latin egoismus, from Latin ego (see ego). Meaning "doing or seeking of that which affords pleasure or advances interest" is from 1800; opposed to altruism, but not necessarily "selfish." Meaning "self-centeredness" is from 1840. Between egoism and egotism, egoism is more correctly formed; there formerly was a useful distinction, with egotism tending to take the senses "self-centeredness" and "extensive use of 'I'" and leaving to egoism the theoretical sense in metaphysics and ethics.