“Blow, Blow, Thou Winter Wind” is a poem from the Shakespeare play As You Like It. This poem is an example of a type of figurative language called personification. When writers personify, they give human characteristics to their subject.
If you look carefully at this poem, you will see that it is not actually about the winter wind at all. Shakespeare reveals his true meaning in the middle of the poem with the line “Most friendship is feigning, most loving mere folly.” He is saying that people are often not true to their “friends” or “loved ones,” or that their friendship or love is not real. He uses the idea of a winter wind, which could be painful, to communicate how much more painful the false love and friendship is. So, when he says of the wind, “Thy tooth is not so keen,” he means that the pain caused by the wind (in the case, the wind’s metaphorical “tooth” can cause pain by biting) is not as hurtful as the emotional pain of the untrue friend or lover.
The personification is evident in the description of the wind. It is said to have a “tooth” and “breath.” It is also said to be less “unkind” than the untrue friend. These are human attributes rather than aspects of the wind. He uses the wind as a contrast to an aspect of human life; therefore, he needs to personify it.