"repetition of the same word, or use of several words conveying the same idea, in the same immediate context; repetition of the same thing in different words; the useless repetition of the same idea or meaning," 1570s, from Late Latin tautologia "representation of the same thing in other words," from Greek tautologia, from tautologos "repeating what has been said," from tauto "the same" (contraction of to auto, with to "the" + auto, see auto-) + -logos "saying," related to legein "to say," from PIE root *leg- (1) "to collect, gather," with derivatives meaning "to speak (to 'pick out words')." Related: Tautological.
Proto-Indo-European root meaning "to collect, gather," with derivatives meaning "to speak" on the notion of "to gather words, to pick out words."
It forms all or part of: alexia; analects; analogous; analogue; analogy; anthology; apologetic; apologue; apology; catalogue; coil; colleague; collect; college; collegial; Decalogue; delegate; dialect; dialogue; diligence; doxology; dyslexia; eclectic; eclogue; elect; election; epilogue; hapax legomenon; homologous; horology; ideologue; idiolect; intelligence; lectern; lectio difficilior; lection; lector; lecture; leech (n.2) "physician;" legacy; legal; legate; legend; legible; legion; legislator; legitimate; lesson; lexicon; ligneous; ligni-; logarithm; logic; logistic; logo-; logogriph; logopoeia; Logos; -logue; -logy; loyal; monologue; neglect; neologism; philology; privilege; prolegomenon; prologue; relegate; sacrilege; select; syllogism; tautology; trilogy.
It is the hypothetical source of/evidence for its existence is provided by: Greek legein "to say, tell, speak, declare; to count," originally, in Homer, "to pick out, select, collect, enumerate;" lexis "speech, diction;" logos "word, speech, thought, account;" Latin legere "to gather, choose, pluck; read," lignum "wood, firewood," literally "that which is gathered," legare "to depute, commission, charge," lex "law" (perhaps "collection of rules"); Albanian mb-ledh "to collect, harvest;" Gothic lisan "to collect, harvest," Lithuanian lesti "to pick, eat picking;" Hittite less-zi "to pick, gather."
mid-15c., "full of pride," from Latin fastidiosus "disdainful, squeamish, exacting," from fastidium "loathing, squeamishness; dislike, aversion; excessive nicety," which is of uncertain origin; perhaps from *fastu-taidiom, a compound of fastus "contempt, arrogance, pride," and taedium "aversion, disgust." Fastus is possibly from PIE *bhars- (1) "projection, bristle, point," on the notion of "prickliness" (Watkins) or "a semantic shift from 'top' to 'haughtiness' which is conceivable, but the u-stem is not attested independently" [de Vaan], who adds that "fastidium would be a tautology." Early use in English was both in passive and active senses. Meaning "squeamish, over-nice" in English emerged 1610s. Related: Fastidiously; fastidiousness.