Jeff sits next to 3 phonetic neighbors — Geoff, Jeb, and Jesse are the closest matches by sound. Most share Jeff's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"divine peace, God's peace"
"from the market town"
"new, fresh"
"short form of Cameron or Camden"
"blue-green color"
"modern invented name"
"pure (via Katharina in Norwegian use)"
"of Sean"
"bear-like strength (if related to arth)"
"garden of hollies, holly garden"
"ease, wealth"
"settlement near rye fields"
"handsome, beautiful"
"smooth, tender"
"of the Saxon people"
"young person, noble youth"
"my inheritance"
"greatest, son of Max"
"noble friend"
"of the earth, ground"
Similar sound: These names share phonetic patterns with Jeff — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Germanic origins, giving them the same cultural heritage as Jeff.
Rhythm: Jeff is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.