Self-efficacy
Etymology
Coined by the psychologist Albert Bandura in 1977 as a central term of his social cognitive theory. It joins "self" with "efficacy," from Latin "efficacia" (effectiveness), from "efficere" (to accomplish). The concept reframed motivation around belief in one’s own capability.
noun · /self-EF-ih-kuh-see/
Your belief in your own ability to succeed at a specific task or situation.
What it names
A useful, targeted concept for the confidence that actually drives effort and persistence — it explains why two equally skilled people attempt very different things depending on what they believe they can pull off.
Example
Small early wins built her self-efficacy, so she started tackling problems she would once have assumed were beyond her.
Related idea
Related to locus of control (already here) but narrower: locus of control asks whether outcomes hinge on you or on fate, while self-efficacy asks whether you specifically can do this particular thing.