Theon sits next to 4 phonetic neighbors — Leon, Deon, and Theron are the closest matches by sound. Most share Theon's Greek-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"godly, divine"
"modern coinage"
"peace through daring"
"fast sailing vessel"
"friend of the gods (Germanic tradition)"
"long-lived, permanent"
"lyric poetry, song set to the lyre"
"of Anthony, son of Anthony (via De- prefix)"
"tube, channel"
"lapis lazuli (the stone)"
"son of Mart (Martin)"
"healer, to heal"
"from the valley"
"spear ruler"
"healer"
"son of Tenney"
"God will strengthen"
"little drop of water"
"shining glory"
"first of the month, calends"
"realm, dominion"
Similar sound: These names share phonetic patterns with Theon — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Greek origins, giving them the same cultural heritage as Theon.
Rhythm: Theon is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.