Definition of nail down

The phrase "nail down" is essentially an expression that refers to making a plan or arrangement definite or secure. Its origin can be traced back to the early 19th century, when it was used in the context of carpentry. In the past, before modern materials like screws and adhesives were widely available, nails were used to join pieces of wood together during construction. When a carpenter needed to attach a piece of wood firmly to another, he would "nail it down" by driving nails into the wood until it was securely fastened. The expression "nail down" was used to describe this process and eventually came to be used as a metaphor for making something certain or secure in other contexts. Over time, the phrase "nail down" has evolved and developed its own unique connotations beyond just physical fastening. Today, it is often used to signify putting an end to uncertainty, making a decision or agreement final, or securing a position or idea. Its origin in carpentry, however, provides a fascinating glimpse into the history of construction techniques and the way language evolves over time.