Since I was said not to have given my own meaning, I am quoting myself in brief excerpts from a paper given in Florence. The following are two excerpts from a paper given but not yet published. so it is not to be quoted without permission.  This is a brief summary, but I was able to trace Eliot's use of this term in many texts where it clearly is connected with the then-common psychological term.  It is not simply an obvious use of the general meaning of "dissociate," nor is it something Eliot was not very familiar with.  For example, The Varieties of Metaphysical Poetry is clearly an allusion to William James's The Varieties of Religious Experience, which Eliot read and annotated.



In the late 19th and 20th century, a dominant medical concept was Pierre Janet's description of hysteria as always a form of dissociation or "a form of mental depression characterized by the retraction of the field of personal consciousness and a tendency to the dissociation of ideas and functions that constitute personality" (Gish 111).[i] It may take many forms, including amnesia; numbness; anaesthesia of all senses; aboulia or loss of will (which Eliot claimed as his own emotional problem); depersonalization, in which the subject experiences the self as unreal or detached from experience or even dead; derealization, in which the external world seems "unreal"; or the extreme form of the double (or dédoublement) in which "a person may actually perceive and even interact with an external double of him-or herself," including dual personality (Gish109). 



In his analysis of The Waste Land as an hysterical text, Wayne Koestenbaum opened up our reading to the ruptures, sexual anxieties and language dysfunction in what had increasingly been read as a unified mythic vision of the modern world.  But Eliot's own language, personal experience, and representations of dissociation suggest that the text's hysteria is more fully understood through Janet than Freud.  It is useful, I think, to note that Eliot went to Roger Vittoz after consulting several friends, that Vittoz's analysis of neurasthenia uses a model comparable to Janet's, and that Eliot specifically claimed in a letter to Sydney Waterlow that Vittoz was not a psychoanalyst "but more useful for my purpose." (L1 495) At this point, December 1921, he was in Lauzanne, "feeling much better," and "trying to finish a poem.

  [i] I have discussed in detail Eliot's knowledge of Janet and use of Janet's concepts in relation to the "dissociation of sensibility."  See "Discarnate Desire: T. S. Eliot and the Poetics of Dissociation" in Works Cited for extended definition and commentary on these terms."