In my career as a lumberjack, I cut down exactly 37,194 trees. I know because I kept a log.
Why this joke works
Make the Number Sound Credible
The oddly precise tree count makes the speaker sound like a careful record keeper. “Log” then means both that record and a cut tree. Read the number deliberately, pause after the claim, and deliver the explanation with confidence. The unnecessary precision helps sell the straight-faced logic. A lumberjack cuts trees into logs, while keeping a log means maintaining a written record of events or totals.
A closer look
A Work Record Is Also a Piece of Timber
The exact total makes the speaker sound unusually confident about a long career. “Kept a log” then appears to explain the bookkeeping, but a log is also what remains after a tree is cut. The joke never states whether the lumberjack wrote anything down or simply kept wood. That ambiguity turns a sensible recordkeeping phrase into an absurdly literal counting method.
Fact behind the joke
Tree Rings Can Preserve a Record of Past Growth
The National Park Service explains that many trees add a growth ring each year. Ring width and structure can reflect age and environmental conditions, and dendrochronology compares patterns among trees to date wood and study the past. A lumberjack’s written log records work intentionally; a physical log may contain a different record created naturally as the tree grew.