Opal sits next to 3 phonetic neighbors — Opel, Opaline, and Coral are the closest matches by sound. Most share Opal's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"precious gemstone"
"torch, shining light"
"poppy flower"
"God is my light"
"of the sea, maritime"
"free woman"
"sea of bitterness"
"victory of the people"
"ring of light"
"nourishing, kind"
"dark red, crimson"
"courageous, valiant"
"to open (spring)"
"from the city of Vienna"
"ruler of supernatural beings"
"joyful"
"beloved, exalted crown"
"dark beauty"
"tailor, cloth-cutter"
Similar sound: These names share phonetic patterns with Opal — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Sanskrit origins, giving them the same cultural heritage as Opal.
Rhythm: Opal is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.