Tegan sits next to 4 phonetic neighbors — Megan, Reagan, and Keegan are the closest matches by sound. Most share Tegan's Welsh cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"darling, beloved treasure"
"dew of heaven, morning dew"
"grace, kindness"
"son of David"
"blonde, yellow-haired"
"courageous, spirited (from Irish Raghallach)"
"fortified hill"
"beneficent, good"
"God is good"
"God is gracious"
"friend, companion"
"awakening"
"blind (saint's epithet)"
"truth"
"west meadow"
"narrow road, pathway between hedges"
"unbranded calf, one who doesn't follow the herd"
"joy, happiness, joyful"
Similar sound: These names share phonetic patterns with Tegan — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Welsh origins, giving them the same cultural heritage as Tegan.
Rhythm: Tegan is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.