Why is the word chef spelled with ch but sounds like sh?

The word "chef" comes from the French word "chef", which is pronounced with a "sh" sound. The "ch" spelling is a remnant of Old French, where the "ch" digraph was pronounced with a "k" sound.

Over time, the pronunciation of "ch" evolved in French, becoming the "sh" sound we know today. However, the spelling remained the same when the word was borrowed into English.

This is similar to other words with "ch" that are pronounced with a "sh" sound, like "machine" and "champagne". These words also reflect the evolution of French pronunciation over time, where the "ch" digraph shifted from a "k" sound to a "sh" sound.