Could you please tell me the meaning of "hollowy" in the following excerpts from the chapter Four and Six of The Great Gatsby? Does it mean "faintly", "with a cavernous voice", or "with a false ring"
a) I took him into the pantry where he looked a little reproachfully at the Finn. Together we scrutinized the twelve lemon cakes from the delicatessen shop.
“Will they do?” I asked.
“Of course, of course! They’re fine!” and he added hollowly, “...old sport.”
b) A massive and lethargic woman, who had been urging Daisy to play golf with her at the local club tomorrow, spoke in Miss Baedeker’s defence:
“Oh, she’s all right now. When she’s had five or six cocktails she always starts screaming like that. I tell her she ought to leave it alone.”
“I do leave it alone,” affirmed the accused hollowly.