Answer:
They highlight Twain's familiarity with the parts of a steamboat, which gives the passage a more authoritative feel.
Step-by-step explanation:
This is the best description of the effect these words have on the text. In this passage, we learn about the names that Twain uses in his description of a steamboat. The variety of names he employs suggest that Twain has great knowledge of the parts of a steamboat, and this gives the passage a more authoritative feel.