A Tom Swiftie, followed by another one on the next page: “‘I don’t sleep,’ said Frost icily, […]”.
Tom Swifties (after the famous series of boys’ novels which popularised them) are sentences of the form “xxx, said he zzz-ly”, where the zzz refers back to the xxx. Examples:
“Pass me the shellfish,” said Tom crabbily.
“Let’s look for another Grail!” Tom requested.
“I used to be a pilot,” Tom explained.
“I’m into homosexual necrophilia,” said Tom in dead earnest.