Jolly sits next to 5 phonetic neighbors — Polly, Holly, and Molly are the closest matches by sound. Most share Jolly's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"merry, festive, cheerful"
"lady, mistress of the house"
"free one"
"heavenly star"
"life, vitality"
"mountain, elevated place"
"from the sea, sea fortress"
"strong wolf, mighty hound"
"of the Verginius family"
"God is gracious; feminine variant of John"
Similar sound: These names share phonetic patterns with Jolly — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old French origins, giving them the same cultural heritage as Jolly.
Rhythm: Jolly is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.