The term 'coaly eyes' is a widely used in description of deep dark eyes amongst Bengali poets. This poem is a tribute to Nazrul Islam, famous Bengali Poet, who begins one of his poems/songs with the same opening line, hence under quotation.
'So much tears in those coaly eyes'
that bleed with every blink
so blink away those coaly eyes
and let your sorrow sink
let it be lost amongst the thoughts that fly away every day
now raise your coaly eyes
High up to the skies
look down at the ground
Look around you and you will find
a pair of eyes that are waiting to be seen
So give in to the sight
that will kindle those coaly eyes that love to blink