en_tn_condensed/hos/07/09.md

Gray hairs are sprinkled on him

Here "gray hairs" represent old age. (See: rc://en/ta/man/translate/figs-metonymy)

but he does not know it

However, this "old age" is clearly a way of saying that the northern kingdom is getting weaker and weaker, because the nation does not know it is "old." (See: rc://en/ta/man/translate/figs-metaphor)