Spencer sits next to 4 phonetic neighbors — Hunter, Carter, and Parker are the closest matches by sound. Most share Spencer's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"dispenser of provisions, household steward"
"God has consoled"
"defender, protector"
"native Hawaiian hardwood tree"
"noble, illustrious"
"king, master"
"battle"
"patrician, of noble birth"
"handsome, beautiful"
"fair, pale, bright"
"from Dax, town settlement"
"the great river"
"battle strength"
"beauty, adornment, grace"
"place of elms"
"growth, abundance"
"exalted, noble, high"
"Finnish person, Norseman"
"protector of mankind"
"little red one (from red hair)"
"man of peace"
Similar sound: These names share phonetic patterns with Spencer — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old French origins, giving them the same cultural heritage as Spencer.
Rhythm: Spencer is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.