diffident
diffident(dis- + fidere) ↔ confident(con- + fidere)
https://gyazo.com/967ae7abd0e9a1a64318ecdc6849ee73
adjective
modest or shy because of a lack of self-confidence:
«…に» 自信のない, 内気な; 気おくれした, 遠慮がちな «about» (↔ confident)
e.g. a diffident youth.
DERIVATIVES
diffidently |ˈdifəd(ə)ntlē| adverb
ORIGIN
late Middle English (in the sense ‘lacking confidence or trust in someone or something’): from Latin diffident- ‘failing in trust’, from the verb diffidere, from dis- (expressing reversal) + fidere ‘to trust’.