Shannon sits next to 3 phonetic neighbors — Sharon, Shannen, and Shan are the closest matches by sound. Most share Shannon's Irish-rooted cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"wise river, old river"
"lapis lazuli blue"
"variant of Shana (God is gracious)"
"brave, valiant (from Ry- element)"
"to esteem, to value (from aestimare)"
"army hill"
"the Italian peninsula"
"crown of laurel"
"red clearing"
"mighty with a spear (ger + wald)"
"dark-complexioned, dark beauty"
"aunt"
"new and graceful"
"determined protector, will to protect"
"protector of men"
"one who walks, traveler"
"devoted to the god of wine and festivity"
"rising, sunrise"
"island, beautiful"
"clear, cloudless"
"each of the two, pure"
Similar sound: These names share phonetic patterns with Shannon — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Irish origins, giving them the same cultural heritage as Shannon.
Rhythm: Shannon is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.