> XAR is pronounced like "czar" (/t͡ʂar/). The 'X' in XAR is meant to be a placeholder for all other letters as at Facebook this format was originally designed to replace ZIP-based PAR (Python archives), JSAR (JavaScript archives), LAR (Lua archives), and so on.

https://pypi.org/project/xar/

One syllable, rhymes with "car" but with a "z" sound ("zar").

Czar?