The name "Shaanxi" is an irregular romanization of the Mandarin pronunciation of the Chinese name meaning "[Land] West of the Shan Pass". This pass in Henan, now part of Sanmenxia's Shanzhou District, was considered to be the place where the Yellow River left the Loess Plateau and entered the North China Plain.
Because the Mandarin pronunciation of Shaanxi and its eastern neighbor Shanxi differ only in tone, their spelling in pinyin romanization differ only by tone marks (Shǎnxī and Shānxī, respectively). The People's Republic of China therefore adopted the special official spelling "Shaanxi". The first syllable is derived from Gwoyeu Romatzyh romanization, which reflects the tones of the words' vowels in their spelling.The second syllable—which would be shi in Gwoyeu Romatzyh is instead given its usual pinyin spelling xi. When tone marks are noted, it is spelled Shǎnxī rather than Shǎanxī or Shaǎnxī.
Before the adoption of pinyin, Shaanxi was romanized as Shensi in the Chinese postal romanization scheme.