Garrulous

Etymology

From Latin garrulus, "talkative, chattering," which comes from the verb garrire, "to chatter or prattle." The Latin verb was partly imitative — meant to sound like the noise of endless small talk, much like our "gab." That flavor survives exactly: garrulous is not just talking a lot but talking on and on about nothing much.

adjective · /GAR-uh-lus/
Excessively talkative, especially about trivial or unimportant things.
What it names
The word for the person who cannot let a silence stand and fills it with rambling, low-stakes chatter that outlasts your patience.
Example
Trapped beside a garrulous seatmate, she learned the man’s entire medical history before the plane had even taxied.
Related idea
Loquacious simply means talkative, often fluently and to a purpose; garrulous carries the extra charge of tedium and triviality.