Casimir sits next to 4 phonetic neighbors — Casimir, Kasimir, and Cazimir are the closest matches by sound. Most share Casimir's Polish-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"proclaimer of peace"
"may God protect"
"born on Sunday"
"he laughs, laughter"
"priceless, of inestimable worth"
"defender (Greek mythological meaning)"
"lord of the marches, march warden"
"may He add another son"
"tumult, riot"
"bright army, famous warrior"
"gentle, lenient"
"symbol of Christian faith"
"protector of mankind"
"home ruler, power"
"guardian of prosperity"
"son of a nobleman (variant interpretation)"
"vigorous, energetic ruler"
Similar sound: These names share phonetic patterns with Casimir — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old Polish Slavic origins, giving them the same cultural heritage as Casimir.
Rhythm: Casimir is a 3-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.