elephantyoudaoicibaDictYouDict[elephant 词源字典]
elephant: [13] Elephants were named from their tusks. Greek eléphās (probably a borrowing from a non-Indo-European language) meant originally ‘ivory’ (hence chryselephantine ‘of gold and ivory’ [19]). Only later did it come to denote the animal itself, and it passed in this sense into Latin as elephantus. By post-classical times this had become *olifantus, and it is a measure of the unfamiliarity of the beast in northern Europe in the first millenium AD that when Old English acquired the word, as olfend, it was used for the ‘camel’.

Old French also had olifant (referring to the ‘elephant’ this time) and passed it on to English as olifaunt. It was not until the 14th century that, under the influence of the classical Latin form, this began to change to elephant. In the 16th and 17th centuries there was a learned revival of the sense ‘ivory’: Alexander Pope, for instance, in his translation of the Odyssey 1725, refers to ‘the handle … with steel and polish’d elephant adorn’d’.

The notion of the white elephant as ‘something unwanted’ arose apparently from the practice of the kings of Siam presenting courtiers who had incurred their displeasure with real white elephants, the cost of whose proper upkeep was ruinously high.
[elephant etymology, elephant origin, 英语词源]
bee's knees (n.)youdaoicibaDictYouDict
1923, a survivor of a fad around this year for slang terms denoting "excellence" and based on animal anatomy. Also existed in the more ribald form bee's nuts. Other versions that lasted through the century are cat's whiskers (1923), cat's pajamas, cat's meow. More obscure examples are canary's tusks, cat's nuts and flea's eyebrows. The fad still had a heartbeat in Britain at the end of the century, as attested by the appearance of dog's bollocks in 1989. Bee's knee was used as far back as 1797 for "something insignificant."
muntjacyoudaoicibaDictYouDict
"A small SE Asian deer, the male of which has tusks, small antlers, and a doglike bark", Late 18th century: from Sundanese minchek.
ProboscideayoudaoicibaDictYouDict
"An order of large mammals that comprises the elephants and their extinct relatives. They are distinguished by the possession of a trunk and tusks", Modern Latin (plural), from proboscis.