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"
"bright fame"
"God is good"
"dweller near the reed meadow"
"courageous, spirited (from Irish Raghallach)"
"high ground"
"fortified hill"
"little child, darling"
"beneficent, good"
"friend, companion"
"precious, little rock"
"heart, mind, spirit"
"dew of heaven, morning dew"
"feminine form of Evan/John"
"heavenly"
"blonde, yellow-haired"
"grace, kindness"
"beloved one's descendant"
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.