They also show the exorcism and purification of impurities, bad vibes that cause illness and other misfortune, devils and disasters as well as kigo (a season word) for haiku (Japanese seventeen-syllable poem).
俳句の季語と同じように、間接的な比喩として穢れ・邪気・魔・厄を、祓い清める事を表している言葉でもある。