Fen sits next to 3 phonetic neighbors — Ben, Ken, and Zen are the closest matches by sound. Most share Fen's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"marsh, boggy ground"
"servant of God"
"to tie, to bind"
"gift of God / gift of Yahweh"
"from the worthy farmstead or settlement"
"wharf, landing place"
"king's meadow; royal clearing"
Similar sound: These names share phonetic patterns with Fen — 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 Fen.
Rhythm: Fen is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.