The quality or state of lacking confidence or self-assurance; a tendency to doubt one's own abilities or worth.
From 'diffident' (Latin 'diffidens,' from 'dis-' meaning not and 'fidere' meaning to trust) plus '-ness,' which creates an abstract noun for personal qualities.
Victorian literature often portrayed characters with 'diffidentness'—their self-doubt and lack of assurance, especially in women, was seen as either charming or frustrating depending on the author's view.
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