symbolyoudaoicibaDictYouDict[symbol 词源字典]
symbol: [15] Etymologically, a symbol is something ‘thrown together’. The word’s ultimate source is Greek sumbállein, a compound verb formed from the prefix sun- ‘together’ and bállein ‘throw’ (source of English ballistic, problem, etc). The notion of ‘throwing or putting things together’ led on to the notion of ‘contrast’, and so sumbállein came to be used for ‘compare’. From it was derived súmbolon, which denoted an ‘identifying token’ – because such tokens were ‘compared’ with a counterpart to make sure they were genuine – and hence an ‘outward sign’ of something.
=> ballistic, parable, parole, problem[symbol etymology, symbol origin, 英语词源]
symbol (n.)youdaoicibaDictYouDict
early 15c., "creed, summary, religious belief," from Late Latin symbolum "creed, token, mark," from Greek symbolon "token, watchword, sign by which one infers; ticket, a permit, license" (the word was applied c.250 by Cyprian of Carthage to the Apostles' Creed, on the notion of the "mark" that distinguishes Christians from pagans), literally "that which is thrown or cast together," from assimilated form of syn- "together" (see syn-) + bole "a throwing, a casting, the stroke of a missile, bolt, beam," from bol-, nominative stem of ballein "to throw" (see ballistics).

The sense evolution in Greek is from "throwing things together" to "contrasting" to "comparing" to "token used in comparisons to determine if something is genuine." Hence, "outward sign" of something. The meaning "something which stands for something else" first recorded 1590 (in "Faerie Queene"). As a written character, 1610s.