Zen sits next to 4 phonetic neighbors — Ben, Ken, and Ten are the closest matches by sound. Most share Zen's Japanese cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"meditation, absorption"
"son of the firebrand"
"pledge, security deposit"
"home on the wooded hill"
"land of Eoghan (short for Tyrone)"
"spear, lance"
"man of power on the hill"
"fire, flame"
"one who lives near the fens or marshes"
"one who helps"
"song, singing bird"
"bright"
"from the hollow"
"power, strength, ruler"
"roof maker"
"noble power, powerful ruler"
"to rejoice, joyful"
"bold counsel, brave advisor"
"resolute protector"
"helmet of will, guardian"
Similar sound: These names share phonetic patterns with Zen — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Sanskrit via Japanese origins, giving them the same cultural heritage as Zen.
Rhythm: Zen is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.