This thesis investigates the roles played by etymology in the work of three late modernist poet-critics: W. H. Auden, J. H. Prynne, and Paul Muldoon. The relationship between poetry and etymology has a long history, but the advent of modern linguistics at the beginning of the twentieth century brought about a change in this relationship. Structuralism developed a more comprehensive condemnation of the etymological fallacy – the view that historical forms and meanings are relevant to current ones - that both isolated etymology as an abstract field of study and undermined its scientific validity. One reaction to this state of affairs has been to re-evaluate etymological discourse itself as poetic or rhetorical. But it is the tension created by what Paula Blank has called 'the quasi-disciplinarity of etymological desire' that motivates Auden, Prynne, and Muldoon's concerns with linguistic historicity. Etymological poetry encourages, even necessitates, very close reading. While this thesis accepts the challenge to read arguably too closely, it also examines the limits of such an approach and its implications for the relationship between poetry and criticism. The first three chapters consider how Auden, Prynne, and Muldoon invoke etymologies in their own criticism, and how etymology affects the ways their poetry may be said to communicate. The second three develop these analyses into new interpretations of commonly debated aspects of their work: Auden's landscape poetry, Prynne's lyricism, and Muldoon's onomastics. It is argued that the fact of obsolescence is key to the etymological poetic; obsolete forms and meanings make poetry difficult, but in the process they intimate that a truer way of representing the world may be (re)discovered. All three poet-critics confront and absorb the consequences of etymological obscurity. Their preoccupation with the history of words is self-consciously and unavoidably pedantic, and it is this pedantry that plays the most significant role in the poetic power they accord to etymology.