The term VALUABLE LOAD FOR A MULE can be broken down into two parts: KILO, which is a 4-letter word, and the rest of the phrase. KILO is a unit of measurement for mass, equal to 1, 000 grams or 2.2 pounds. The phrase 'valuable load for a mule' refers to the fact that mules are often used to carry heavy loads, such as goods or supplies, over long distances. Therefore, the term VALUABLE LOAD FOR A MULE could be interpreted as a metaphor for something that is of great value and worth carrying.