Ny welsei neb o’r ynyssed gynt eu kyfreu. : Not one of the islands had seen such before
ny/ni, nyd/nid : (Verbalpartikel, Negation, Hauptsätze)
welsei (hier leniert 3. P. Sg. Plusquamperfekt von gwelaf: gweld, gweled) : to see, provide, arrange
neb : any; any one, someone
o : (Präposition)
_'r : (Bestimmter Artikel)
ynys (pl. ynyssedd, f) : island
cynt : formerly, before
eu : (Possessivpronomen 3. P. Plural)
kyfreu, cyfrwy : the same kind; similar, like, such