Blu sits next to 4 phonetic neighbors — Blue, Bleu, and Beau are the closest matches by sound. Most share Blu's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"the color blue, sky"
"of the valley"
"one of free status"
"rejoice, be glad (via Gaius/Caio)"
"one who raids, bold adventurer"
"ash tree clearing"
"venerable, great"
"modern variant of Milan/Milen"
"modern invented name variant"
"elf ruler"
"from Grantham"
"son of Rollin, son of Roland"
"of Anthony, son of Anthony (via De- prefix)"
"beautiful mountain"
"new settlement"
"island meadow"
"anointed one"
"lunar, bright as the moon"
"unbranded steer (original meaning)"
"royal town or manor"
"man of the forest"
Similar sound: These names share phonetic patterns with Blu — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old French 'bleu' via Germanic origins, giving them the same cultural heritage as Blu.
Rhythm: Blu is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.