Glen sits next to 4 phonetic neighbors — Glenn, Glyn, and Bren are the closest matches by sound. Most share Glen's Scottish cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"narrow valley, mountain valley"
"promised land, holy city"
"cold, enduring"
"gift of God (via Welsh David)"
"of noble birth"
"home ruler, lord of the estate"
"At the byres, near the cattle sheds"
"who is like God (form of Michael)"
"fiery one"
"son of Gerald"
"standalone phonetic name derived from letter sounds"
"of Mars, warrior"
"man of vigor, strong man"
"modern creative name blend"
"broad hillside"
"variant of Garrett/Gerald"
"eminent marrow"
"man of Rome"
"son"
"forest friend, house friend"
Similar sound: These names share phonetic patterns with Glen — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Scottish Gaelic origins, giving them the same cultural heritage as Glen.
Rhythm: Glen is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.