Modern Welsh coinage, composed of the vocabulary words glân ‘clean, pure, holy’ + da ‘good’. It is also used outside Wales, and is associated particularly with the actress and politician Glenda Jackson (b. 1937).
English: habitational name from a place in Devon recorded in 1291 as Elleford ‘elder tree (Old English ellen) ford’; tūn ‘village’ is a later addition. Alternatively, the surname may have be from Yelverton in Norfolk, which is probably from the personal name Geldfriþ + Old English tūn ‘village’, ‘settlement’.