Results for label
typo3_label_lookup
Reads labels from the installation. Where that cannot boot, the tool reads the package files instead and says which labels that leaves out.

The package registry, read while the installation will not boot
The fallback returns every declared entry — labels among them — and none of the dynamically registered ones. The shortfall travels with the result.

Label overrides resolve before the extension loads
A label from TypoScript that an extension overrides now resolves in the order the core documents, which changed in 13.4.
reference Documentation · Toolstypo3_icon_lookup
Returns the identifier the core itself uses. The label of an icon is not part of the answer — identifiers are what the registry holds.
The sources searched
Four sources, and the last of them is your own installation — in the search only where one is in reach. A facet that says zero got the question; a facet that is absent was never available.