Joan sits next to 3 phonetic neighbors — John, Juan, and Jon are the closest matches by sound. Most share Joan's Spanish-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"God is gracious"
"father of peace"
"dark-skinned, Moorish"
"God enlightens, he shines"
"ruler of the people"
"oak grove, great"
"strong, virtuous, honorable"
"spear ruler (from Gerald)"
"the greatest, the largest"
"ruler of the army (Scandinavian form)"
"God has been gracious"
"roofer, one who covers"
"near the holly trees"
"fragrant, sweet-smelling"
"brave in power"
"noble power, powerful ruler"
"great fort, spacious hill"
"land bordering the sea"
"supplanter (from Jacob/James)"
"wolf"
"foreigner, Welshman (Celtic speaker)"
Similar sound: These names share phonetic patterns with Joan — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Hebrew origins, giving them the same cultural heritage as Joan.
Rhythm: Joan is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.