sestertium
noun
ses·ter·tium se-ˈstər-sh(ē-)əm 
plural sestertia se-ˈstər-sh(ē-)ə
: a unit of value in ancient Rome equal to 1000 sesterces
Word History
Etymology
Latin, from genitive plural of sestertius (in the phrase milia sestertium thousands of sesterces)
First Known Use
1540, in the meaning defined above