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, licence" (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" (from PIE root *gwele- "to throw, reach").
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.
word-forming element making nouns implying a practice, system, doctrine, etc., from French -isme or directly from Latin -isma, -ismus (source also of Italian, Spanish -ismo, Dutch, German -ismus), from Greek -ismos, noun ending signifying the practice or teaching of a thing, from the stem of verbs in -izein, a verb-forming element denoting the doing of the noun or adjective to which it is attached. For distinction of use, see -ity. The related Greek suffix -isma(t)- affects some forms.
1580s, from symbol + -ist. From 1888 in reference to a literary movement that aimed at representing ideas and emotions by indirect suggestion rather than direct expression, from French symboliste, coined 1885 by poet Paul Verlaine (1844-1896). Rejecting realism and naturalism, they attached symbolic meaning to certain objects, words, etc.
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Definitions of symbolism from WordNet
a system of symbols and symbolic representations;
the practice of investing things with symbolic meaning;