The original term of was descriptive of lower-class people who performed manual labor.

The correct answer would be "coolie" as it was used to connote somebody who performs thankless, backbreaking physical labor. The word is often explained as being part of the indentured labor system that followed the abolition of slavery in the 1800s, particularly gaining popularity in the mid- to late-1800s. It is often almost exclusively used in relation to Asian laborers, especially Indian and Chinese people.