Where does the name Qatar come from?
Does Qatar have a meaning?
What does Qatar mean? - Quora. Notably, the word قطر (that is, Qatar) is found in two math terms: qatar al-daa'ira (meaning 'diameter') and nusf al-qatar (meaning 'radius'; literally, 'half-diameter').
The word ‘qatar’ also refers to the scrappy little emirate sticking out of the Arabian Peninsula into the Persian Gulf, recently become a bit more popular than usual thanks to a recent lovers’ spat between it and most of its neighbors.

Its name probably has nothing to do with the Arabic word for ‘diameter’, and more likely stems from a substrate language dating to before the Arabian conquest. At least, in pre-Islamic Greek sources, the peninsula was referred to as Katara, so it’s possible that the name is not ultimately Arab in origin. According to Houssam Ahmed, there's speculation that the word meant 'a drop of water’ in one of those substrate languages, but we can never be certain.