Likely a modern variation of Zianna or Ziana
Zyannah is a contemporary American name, likely created as a creative blend or phonetic variation of names like Ziana, Ayanna, or Gianna. Because it is a modern invention, it does not have a single traditional etymological root, but it often carries the 'grace' or 'flower' associations of its sound-alike counterparts.
Less common today
Zyannah isn't in the latest US Top 1000. It last peaked at #13,309 in 2012.
US births per 5-year period, 1990βpresent (SSA data).