Appeal to authority
Etymology
The Latin name "argumentum ad verecundiam," coined by John Locke, means an appeal "to modesty" or reverence — "verecundia," the shame one feels in contradicting the eminent. Locke’s point was that respect for authority can shame us out of thinking for ourselves. The fallacy is not citing experts but treating their say-so as beyond question, or borrowing authority from the wrong field.
noun phrase · /uh-PEEL too aw-THOR-ih-tee/
Treating a claim as true simply because an authority endorses it, especially one outside their expertise.
What it names
Spotting it distinguishes citing genuine, relevant expertise from leaning on prestige as a substitute for evidence.
Example
"A famous physicist says this diet works, so it must" is an appeal to authority — nutrition isn’t his field.
Related idea
The mirror image is the genetic fallacy, which judges a claim by its source to dismiss it rather than to endorse it.