Shannan sits next to 4 phonetic neighbors — Shannon, Shanan, and Cannon are the closest matches by sound. Most share Shannan's Irish-rooted cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"old river, ancient waters"
"resolute protector who adds blessings"
"adventurous, wanderer"
"label, identifying mark; to touch lightly"
"God is gracious"
"high, noble"
"narrow strait or channel"
"fond of horses"
"eminence, hill"
"to tame, subdue"
"shield wolf, brave protector"
"grey, grey-haired"
"I awake, I am awake"
"noble kind"
"shield wolf (derived from Randy/Randolph)"
"invented name with La- prefix (the) and Voris (from the ford, Dutch..."
"who is like God?"
Similar sound: These names share phonetic patterns with Shannan — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old Irish origins, giving them the same cultural heritage as Shannan.
Rhythm: Shannan is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.