Rio sits next to 4 phonetic neighbors — Leo, Theo, and Nico are the closest matches by sound. Most share Rio's Spanish-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"river"
"to rejoice, joyful"
"saved by God"
"nobleman, duke"
"gift, from the sea"
"God's helper (ezer + El)"
"God the highest (variant interpretation)"
"servant of God"
"statement of belief, system of faith"
"strong spear-fighter"
"firebrand"
"young lion"
"selected, set apart, elected"
"lover of hounds, hound-desiring"
"from Brix (place name)"
"the one to whom it belongs"
"protector of mankind"
"little warrior, war-associated"
"sun, like the sun"
"brave, manly"
"modern elaboration of Jason"
Similar sound: These names share phonetic patterns with Rio — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Spanish/Portuguese origins, giving them the same cultural heritage as Rio.
Rhythm: Rio is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.