Metonymy
Etymology
From Greek metōnymía, "a change of name": meta ("change") + ónyma, a dialect form of ónoma ("name"). The literal sense is swapping one name for a neighboring one. Rhetoricians kept it precise — the substitute has to be genuinely linked to its target (crown for monarchy, the press for journalism), not merely similar.
noun · /muh-TON-uh-mee/
Referring to something by the name of a thing closely associated with it rather than the thing itself.
What it names
The shorthand that lets "the White House said" stand in for a president and staff — naming by association, which compresses a whole institution into one handy label.
Example
When a reporter writes that "Silicon Valley is nervous," the metonymy folds thousands of companies into a single place-name.
Related idea
Synecdoche is the tighter case where the associated thing is literally a part of the whole — "all hands on deck." Metonymy links by association; synecdoche links by membership.