Johan sits next to 4 phonetic neighbors — Joanna, Johanna, and Joan are the closest matches by sound. Most share Johan's Dutch-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"God is gracious"
"settlement of Beorhtel people (Burlington origin)"
"lilac, bluish"
"tuft, bump, rounded protrusion"
"from the Frankish people, free"
"modern coinages with no fixed etymology"
"bare hill"
"dear friend"
"spear ruler"
"the dawn, daybreak"
"God is gracious (from Jean component)"
"elaboration of Audrey with French -ene suffix"
"variant of diminutive feminine names"
"little Jon, feminine form of Jon"
"noble, patrician"
"Little Rome or of Rome; Italian diminutive of Roma"
"alder tree grove (from Gaulish via Vernon)"
Similar sound: These names share phonetic patterns with Johan — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Hebrew Yohanan origins, giving them the same cultural heritage as Johan.
Rhythm: Johan is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.