Gracious
Jahnya is a modern American creation, likely a phonetic variation of Janiyah or a blend of the Hebrew name Jah (referring to God) with the popular 'nya' suffix. It carries the spiritual connotation of divine favor and grace. While rare, it fits within the trend of melodic, multi-syllabic names ending in 'a'.
Less common today
Jahnya isn't in the latest US Top 1000. It last peaked at #5,916 in 2008.
US births per 5-year period, 1990βpresent (SSA data).