Sissy Spacek nows.
I think they’re just trying to narrow down exactly what they think it is–movement with the mind rather than just movement at a distance. You’ll find a lot of semantical activity when it comes to pseudoscience. It seems more scientific and distracts from the lack of data supporting such phenomena.
In addition to pd’s answer, I also think it’s a reaction to the skeptical response to all things psychic. “Psych” is a very authoritative, scientific-sounding prefix — psychology, psychoanalysis, psychiatry, psychosis, psyche, psychotherapy, etc. Renaming telekinesis using the “psych” prefix probably was partially motivated by the desire to make telekinesis seem more scientific and reasonable.
Psychokinesis literally means “mind motion”.
Telekinesis literally means “distant motion”, or “motion at a distance”.
They are used equivalently to describe the same non-existent phenomenon.
That is an interesting question (star to you). I don’t think there is any obvious answer but I will speculate.
Telekinesis (TK) means motion at a distant. Thus any mechanism (say a persons eyes) could be the cause of this motion of a object at a distant. Where the word psychokinesis (PK) suggest (as the theory now suggest) that the consciousness/mind is the force behind the object being moved. Thus, the word more accurately reflects the theory.