The riddle
What Do You Call an Alligator in a Vest?
Checking the sounds
Spell the answer: invest-igator. The first part reads "in vest", the words of the question. The ending, igator, is also the ending of alligator, which is spelled all-igator. So both words finish in the same six letters, and the riddle joins "in a vest" to the back of the animal's name. Merriam-Webster gives investigator the pronunciation in-VES-tuh-gay-ter and alligator AL-uh-gay-ter, so the ends match and the middle blurs a little. The joke works as a fast sound-alike, not an exact one.
Not the same vest
The vest in investigator is not a piece of clothing. Investigate comes from a Latin verb meaning to track, built on vestigium, a footprint (Merriam-Webster). The garment called a vest comes from a different Latin word for clothing. The pun joins two words that merely look alike on the page.
Where the animal got its name
Alligator comes from the Spanish el lagarto, meaning the lizard (Merriam-Webster). English speakers took the article and the noun together and turned them into one word. It is a handy reminder that a word's first use is often not its final form.
Reading the answer aloud
Say the question slowly so that "in a vest" has its own beat, then say the answer with a lean on the middle syllable. Listeners who mishear it as "in-vest-alligator" usually understand at once. A magnifying glass and a notebook, held up as props, help the very young see what an investigator does. The Latin root also gives English the word vestige, a trace left behind (Merriam-Webster), which fits an investigator who follows traces.