Cognitive dissonance
Etymology
"Cognitive" is from Latin cognoscere, "to know"; "dissonance" is from dissonare, "to sound discordant" (dis-, "apart," + sonare, "to sound"). So the phrase is literally two thoughts that don’t sound right together. The psychologist Leon Festinger named the effect in 1957.
noun · /KOG-nih-tiv DIS-uh-nunce/
The mental discomfort of holding two conflicting beliefs, or acting against what you believe.
What it names
The squirm that pushes us to rationalize — and why people often change their story rather than their behavior.
Example
Buying the gas-guzzler he’d spent years criticizing left him with real cognitive dissonance — quickly resolved by deciding the criticism was overblown.
Related idea
Rationalization is the usual cure we reach for; motivated reasoning is the broader habit.