To whet something means to sharpen it, especially a blade. A chef might whet a dull knife on a whetstone, a special rough stone designed for sharpening. The repeated sliding motion against the stone grinds away tiny bits of metal, creating a razor-sharp edge. Before modern knife sharpeners existed, people whetted their knives, axes, and scythes this way to keep them effective.

The word also means to stimulate or increase an appetite or desire. A delicious smell wafting from the kitchen whets your appetite for dinner. Reading the first chapter of an exciting book whets your curiosity about what happens next. A preview of coming attractions at the movie theater is designed to whet your interest in upcoming films.

When you whet someone's appetite or curiosity, you're sharpening their desire the same way you'd sharpen a blade, making it keener and more intense. The word suggests making something that was already there become stronger and more focused, ready for what comes next.