sycophantyoudaoicibaDictYouDict[sycophant 词源字典]
sycophant: [16] Sycophants are etymologically ‘fig-showers’. The word comes via Latin sychophanta from Greek súkophántēs, a compound formed from súkon ‘fig’ and -phántēs ‘shower’, a derivative of phaínein ‘show’ (source of English fancy, phantom, etc). Súkon (which probably came from a Semitic source that also produced Latin ficus ‘fig’, source of English fig) was used metaphorically for ‘cunt’, and hence for an ‘indecent gesture made by putting the thumb into the mouth or between two fingers’.

People who grassed on criminals were said to ‘show them the fig’ – ‘show them two fingers’, as it might be expressed in modern English. And so the term súkophántēs came to be used for an ‘informer’, and eventually, via ‘one who ingratiates himself by informing’, for a ‘flatterer’ or ‘toady’.
=> fancy, phantom, sycamore[sycophant etymology, sycophant origin, 英语词源]
sycophant (n.)youdaoicibaDictYouDict
1530s (in Latin form sycophanta), "informer, talebearer, slanderer," from Middle French sycophante and directly from Latin sycophanta, from Greek sykophantes "false accuser, slanderer," literally "one who shows the fig," from sykon "fig" (see fig) + phainein "to show" (see phantasm). "Showing the fig" was a vulgar gesture made by sticking the thumb between two fingers, a display which vaguely resembles a fig, itself symbolic of a vagina (sykon also meant "vulva"). The modern accepted explanation is that prominent politicians in ancient Greece held aloof from such inflammatory gestures, but privately urged their followers to taunt their opponents. The sense of "mean, servile flatterer" is first recorded in English 1570s.
The explanation, long current, that it orig. meant an informer against the unlawful exportation of figs cannot be substantiated. [OED]