Words related to doubt
Proto-Indo-European root meaning "two."
It forms all or part of: anadiplosis; balance; barouche; between; betwixt; bezel; bi-; binary; bis-; biscuit; combination; combine; deuce; deuterium; Deuteronomy; di- (1) "two, double, twice;" dia-; dichotomy; digraph; dimity; diode; diphthong; diploid; diploma; diplomacy; diplomat; diplomatic; diplodocus; double; doublet; doubloon; doubt; dozen; dual; dubious; duet; duo; duodecimal; duplex; duplicate; duplicity; dyad; epididymis; hendiadys; pinochle; praseodymium; redoubtable; twain; twelfth; twelve; twenty; twi-; twice; twig; twilight; twill; twin; twine; twist; 'twixt; two; twofold; zwieback.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit dvau, Avestan dva, Greek duo, Latin duo, Old Welsh dou, Lithuanian dvi, Old Church Slavonic duva, Old English twa, twegen, German zwei, Gothic twai "two;" first element in Hittite ta-ugash "two years old."
1540s, "puzzling, occasioning doubt or uncertainty;" 1630s, "doubtful, hesitating in opinion;" from Late Latin dubiosus "doubtful," from Latin dubium "doubt," neuter of dubius "vacillating, moving two ways, fluctuating;" figuratively "wavering in opinion, doubting, doubtful," from duo "two" (from PIE root *dwo- "two"), with a sense of "of two minds, undecided between two things." Old English also used tweo "two" to mean "doubt." Compare doubt (v.). Related: Dubiously; dubiousness.
1530s, "to have doubts (of the reality of), to suspect, to regard (the truth or reality of) with suspicion," from mis- (1) "badly, wrongly" + doubt (v.). Meaning "to fear or suspect (the existence of something evil) is from 1560s. Intransitive sense of "entertain doubt" is from 1630s. Related: Misdoubted; misdoubting. As a noun, "irresolution," 1590s.
late 14c., of persons, "worthy of honor, venerable" (a sense now obsolete); late 15c., "that is to be dreaded or feared, formidable, terrible," also often "valiant," from Old French redoutable (12c.), from redouter "to dread," from re-, intensive prefix, + douter "be afraid of" (see doubt (v.)).
The verb also was in Middle English, redouten, "to fear, dread; stand in awe or apprehension of; honor" (late 14c., from Old French) and was used through 19c., though OED marks it "now rhetorical."
late 14c., "causing doubt, not distinct in character, meaning, or appearance," from doubt (n.) + -ful. From c. 1400 as "of uncertain issue, precarious." From early 15c. as "full of doubt, having doubt, hesitant, wavering." By mid-15c. as "admitting or subject to doubt." Related: Doubtfully; doubtfulness.
Other words that have been used in English in some or all of these senses were doubtous "undetermined" (mid-14c.); doutive "filled with doubt" (late 14c.); douty "ambiguous, enigmatic, obscure" (late 14c.); doubtable (c. 1400); doubtsome (1510s).
"without doubt, without objection or uncertainty," late 14c., from doubt (n.) + -less. From late 14c. as an adjective, "beyond dispute, certain;" from mid-15c. as "free from doubt." Later in a weakened sense, indicating merely something that to the speaker seems likely to be true. Related: Doubtlessly.