戈壁 itself is a Mongolian loanword (govĭ, 'desert / waterless place'). Adding
滩 (tān, 'flat expanse / shoal') gives the spread-out feel of the landscape. The Gobi straddles northern China (Inner Mongolia, Gansu, Xinjiang) and southern Mongolia. Unlike the Sahara, it's mostly stony / gravel desert, not sand dunes.
