Allan sits next to 4 phonetic neighbors — Alan, Allen, and Alvin are the closest matches by sound. Most share Allan's Scottish cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"rock, harmony"
"born at dawn"
"modern coined name, son of Bray"
"my strength is Yahweh"
"love and goodness"
"supplanter's son"
"son of the praised one"
"beautiful friend, fair friend"
"treasure, to store (possible Arabic root)"
"wealthy guardian"
"wild rose bush"
"aspen tree, quaking poplar"
"ash tree settlement"
"Trent's town, settlement on the Trent"
"free man"
"high, noble"
"protector of people"
"descendant of Madan (little dog)"
"God will add, God will increase"
"priceless one"
Similar sound: These names share phonetic patterns with Allan — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Celtic/Brythonic origins, giving them the same cultural heritage as Allan.
Rhythm: Allan is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.