Sonja sits next to 3 phonetic neighbors — Sonya, Sonia, and Tonja are the closest matches by sound. Most share Sonja's Russian-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"wisdom, skill"
"victory, triumph"
"strong, resilient one"
"sky meadow"
"this world's beauty"
"of noble kind"
"maiden, girl"
"bringer of victory"
"noble one, of noble kind"
"battle woman, warrior"
"beautiful shield, shield rim"
"pure, clear"
"lily flower"
"lapis lazuli, apple"
"bearer of good news"
"consecrated, sacred"
"enchanting, luring"
"gracious gift of God"
"God is my oath (as diminutive of Elizabeth)"
Similar sound: These names share phonetic patterns with Sonja — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Greek origins, giving them the same cultural heritage as Sonja.
Rhythm: Sonja is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.