Day sits next to 5 phonetic neighbors — Dae, Dei, and Ray are the closest matches by sound. Most share Day's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"daylight, the day"
"from the flowering place"
"loving, affectionate (if from Philemon)"
"little raven"
"sunray, shining light"
"The great; the large"
"olive tree; symbol of peace and wisdom"
"noble, nobility"
"from the alder grove"
"eagle"
"the strait, narrow waterway"
"black and blue-green"
"elder counsel"
"stony forest"
Similar sound: These names share phonetic patterns with Day — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old English origins, giving them the same cultural heritage as Day.
Rhythm: Day is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.