The term "grand" is used to mean a thousand dollars. It originated as American slang in the early 1900s, likely derived from the expression "a grand sum of money" to refer to $1,000 [2]. The exact origin of the phrase is unknown, as is often the case with etymology. However, the earliest written usage of "grand" in this context dates back to around 1915 [2].

The usage of "grand" to mean a thousand dollars became so popular that it was eventually abbreviated to "G" or "G-note" [2]. During World War II, American soldiers brought the term to the UK, where it came to mean £1,000 [2]. By the late 1940s, "grand" had expanded its meaning to represent a thousand of almost anything, not just money [2].

It is worth noting that "grand" still retains its other meanings, such as "grand old flag" or "grandparents," which can cause confusion for non-native English speakers [2].

Other terms that refer to a thousand include "thou," which was first recorded in 1869 and is still in use, and "K," short for kilo, which is the Greek prefix for thousand [2]. However, in the world of computers, "K" can sometimes mean 1,024 instead of 1,000, leading to confusion [2].

Learn more:

1. Why does “grand” mean thousand? - Quora
2. What’s the origin of “grand” meaning $1,000? - The Straight Dope
3. british english - Why is 1000$ called a 'grand'? - English Language Learners Stack Exchange