Aberdare Boys’ Grammar School
The School Motto: Gorau Llyw Dysg
The school motto can be translated as ‘Knowledge (or Learning) is the surest (or best) guide (or lead / leader / rudder)’.
This version of the school badge is from the 1965 edition of The Aberdarian. You might notice that the shield above, taken from the title page inside, spells this motto as ‘Gorau Llyw Dysg’.
Gorau is the superlative form of the adjective ‘da’ (good) as in: Da (good) Gwell (better) Gorau (best). Goreu is simply an old, even archaic, form of ‘gorau’. Welsh orthography was the subject of much debate well into the 19th century, there being no government or official usage to suggest norms. They tended to be provided by the Bible, translated in the 16th C and updated in the early 17th C and still in common usage until 1988.
Thanks to Hywel J. Davies for this interpretation.