Design Nomenclature / Type
Ink trap
Also called ink trap, notch
A notch cut out of a join — where shoulder meets stem, or at a tight crotch — so that ink spreading on absorbent paper fills it rather than blotting the join shut. A production countermeasure for hot-metal and newsprint conditions that no longer obtain at high resolution.
In practice
Now mostly worn as a style. That's fine, but a trap drawn to be seen at 96px is not doing the job the name describes, and calling it a trap at display size is decoration wearing engineering's clothes.