Sheppard sits next to 4 phonetic neighbors — Shepherd, Shepard, and Shephard are the closest matches by sound. Most share Sheppard's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"herder of sheep, shepherd"
"man, husband"
"gate keeper"
"son of him who abounds in furrows"
"from the Leyden region"
"dark-haired one"
"victorious people"
"glorious protector (as diminutive of Branislav)"
"modern American coinage"
"strong fighter (from bar + hard)"
"army ruler, commander"
"prince, noble one"
"sad"
"air, breath of life"
"truly brave, genuinely bold"
"son of Hans"
"sun and sea (Hawaiian compound)"
"settlement of Brice"
"son of Rip (surname derivative)"
"handsome, born of fire"
"morning glory, morning well (depending on kanji)"
Similar sound: These names share phonetic patterns with Sheppard — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old English origins, giving them the same cultural heritage as Sheppard.
Rhythm: Sheppard is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.