Philately, Philandering and Philtrum

Philately: Stamp collecting.

Philandering: Sexual fooling around.

Philtrum: The vertical groove between the upper lip and the nose.

"Especially if there was philately going on."
"That'd be philandering," Lucas said. "Philately is stamp-collecting."
"That's what I meant - stamp-collecting."
Lucas scrubbed an index finger across his philtrum.

Within five lines, the author uses philately, philandering and philtrum. I can see him staring at one dictionary page and challenging himself to use three words from that page.