exploityoudaoicibaDictYouDict[exploit 词源字典]
exploit: [14] Latin explicāre (source of English explicate and explicit) meant ‘unfold’. A Vulgar Latin descendant of its past participle was *explictum ‘something unfolded’, which passed into Old French as exploit or esplait. In the process, the original sense of ‘unfolding’ had developed through ‘bringing out, development’ and ‘advantage, success’ to ‘achievement’.

In the case of the English noun, it is the latter meaning which has survived, and in fact originally the verb too denoted ‘achieve, accomplish’. This seems to have died out in the 18th century, however, and when the verb reappears in the 19th century it is closer to the earlier ‘develop’ in meaning, particularly as applied to ‘getting the most out of’ natural resources. The modern derogatory sense ‘use for one’s own selfish ends’ emerged from this.
=> explicit, fold, ply[exploit etymology, exploit origin, 英语词源]
itself (pron.)youdaoicibaDictYouDict
late 14c., from Old English hit sylf, from it + self. Since 17c. usually regarded as its self (compare its own self).
narcissism (n.)youdaoicibaDictYouDict
1905, from German Narzissismus, coined 1899 (in "Die sexuellen Perversitäten"), by German psychiatrist Paul Näcke (1851-1913), on a comparison suggested 1898 by Havelock Ellis, from Greek Narkissos, name of a beautiful youth in mythology (Ovid, "Metamorphoses," iii.370) who fell in love with his own reflection in a spring and was turned to the flower narcissus (q.v.). Coleridge used the word in a letter from 1822.
But already Krishna, enamoured of himself, had resolved to experience lust for his own self; he manifested his own Nature in the cow-herd girls and enjoyed them." [Karapatri, "Lingopasana-rahasya," Siddhanta, II, 1941-2]
Sometimes erroneously as narcism.
selfish (adj.)youdaoicibaDictYouDict
1630s, from self- + -ish. Said in Hacket's life of Archbishop Williams (1693) to have been coined by Presbyterians. In the 17c., synonyms included self-seeking (1620s), self-ended and self-ful.
Let us understand what our own selfish genes are up to, because we may then at least have the chance to upset their designs. [Richard Dawkins, "The Selfish Gene," 1976]
Related: Selfishly; selfishness. Similar formations in German selbstisch, Swedish sjelfvisk, Danish selvisk.