The English word
DEMITASSE is a borrowing from French, meaning "half-cup,"
demi+tasse. The French word is in turn from the Arabic
tassah, from Persian
tasht, meaning a cup or a saucer. (Compare Italian
tazza and Spanish
taza.)
The noun demitasse is also used attributively as, for example, in the phrase "demitasse spoon."
The image below shows a demitasse cup of espresso: