Anderson sits next to 4 phonetic neighbors — Henderson, Jefferson, and Emerson are the closest matches by sound. Most share Anderson's Scottish cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"son of Andrew (manly)"
"son of Armand, warrior"
"kingly, of royal blood"
"from Lucania"
"messenger, herald"
"son of Hendrik"
"river that swallows all rivers"
"valley settlement"
"dispenser of provisions, household steward"
"kingly"
"best"
"poet"
"one who lives near the wells or springs"
"rising in the sky, boundary"
"truly brave, genuinely bold"
"fortunate, good"
"wealthy companion"
"he has heard, God has heard"
"speckled, freckled"
"Currency"
"fallow land, uncultivated land"
Similar sound: These names share phonetic patterns with Anderson — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Scottish/Scandinavian patronymic origins, giving them the same cultural heritage as Anderson.
Rhythm: Anderson is a 3-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.