Wiliam sits next to 4 phonetic neighbors — William, Willem, and Wilhem are the closest matches by sound. Most share Wiliam's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"resolute protector, determined guardian"
"to tame (via Damian root)"
"possibly inspired by Zion, meaning monument or raised up"
"name of God"
"surname used as given name"
"slender, narrow (from Irish Caolan)"
"ruler, king (from -rick suffix)"
"variant of Amal, meaning work or action"
"descendant of Donndubhan"
"loyal, faithful"
"speech, language, of God"
"glory of Hera"
"strength, authority, force"
"staff of the Goths"
"narrow (place name origin)"
"beautiful in character"
"occupational surname turned first name"
"salmon"
"modern invented name, combination of Tae and -vion"
"God is gracious"
"forever, always + wind/fighter (Ey + vindr etymology)"
Similar sound: These names share phonetic patterns with Wiliam — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old High German Willahelm origins, giving them the same cultural heritage as Wiliam.
Rhythm: Wiliam is a 3-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.