In the deserted village the phrases, "laboring swain," "sheltered cot," and "mirthful land," are examples of diction.

In the deserted village the phrases, "laboring swain," "sheltered cot," and "mirthful land," are examples of poetic diction.
This is the way that many poets and writers choose to speak in their works so as to achieve a poetic feeling and atmosphere. Although these combinations of words may not necessarily be used in real language, they sure do sound nice.