Loquacious
Etymology
From Latin "loquax" ("talkative"), from "loqui" ("to speak") — the same root behind "eloquent," "colloquial," and "soliloquy." It entered English in the 17th century.
adjective · /loh-KWAY-shus/
Very talkative; inclined to talk a great deal.
What it names
A precise, slightly formal word for the person who talks freely and at length — more neutral than "chatty," more elegant than "big mouth."
Example
Their loquacious guide narrated every stone of the old town, whether they asked or not.
Related idea
Garrulous carries a stronger note of tiresome rambling; loquacious is more neutral — abundant talk that isn’t necessarily annoying.