Hilary sits next to 4 phonetic neighbors — Hillary, Hilary, and Ellery are the closest matches by sound. Most share Hilary's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"cheerful, merry, joyful"
"source of joy"
"calm, peaceful waters"
"gift of God"
"divine, belonging to heaven"
"she is my delight, pleasant"
"woodland clearing settlement"
"beautiful rose (folk etymology)"
"oneness, harmony, togetherness"
"bright, clear, luminous"
"celestial, of the heavens"
"crown, wreath, garland"
"from Zaria (city in Nigeria)"
"feminine form of Simon"
"descendant of the dark challenger"
"cinnamon, cassia tree"
"joyful, playful"
"to attract powerfully"
"halo of the moon, moonlit"
"light, radiance, splendor"
Similar sound: These names share phonetic patterns with Hilary — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Latin origins, giving them the same cultural heritage as Hilary.
Rhythm: Hilary is a 3-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.