Oleander sits next to 3 phonetic neighbors — Alexander, Leander, and Orlando are the closest matches by sound. Most share Oleander's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"olive tree + man (Greek etymology)"
"mythical guardian creature"
"elf army (alternative theory)"
"hay valley, hedged valley"
"son of Andrew"
"rich, wealthy"
"from the place of the sturgeon"
"a rousing song of praise or national identity"
"noble, exalted"
"foot (of Orion)"
"charcoal hill"
"God grants blessing to the sorrowful"
"small songbird of the meadow"
"worthy of being told in stories"
"water sprite, water spirit"
"tournament fighter, gladiator"
"wise protector"
"state of being free, liberty"
"divine protection"
"Brock's settlement (place name origin)"
Similar sound: These names share phonetic patterns with Oleander — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Greek origins, giving them the same cultural heritage as Oleander.
Rhythm: Oleander is a 4-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.