A term invented and developed in the course of three-way correspondence between US fans Dean Grennell, Redd Boggs and Robert Silverberg circa late 1940s or early 1950s. Dick Eney's Fancyclopedia II states that 'croggle' combines the words 'crush' & 'goggle', although Grennell himself says it is a combination of 'crumble' & 'joggle'. Eney implies it is a noun, one which describes the state of having been "shocked into momentary physical or mental paralysis".
Harry Warner Jr., on the other hand, in his A Wealth of Fable (first version published 1976, but bear in mind Warner's career in fandom began much earlier than Eney's) declares 'croggle' "is normally a verb signifying intense disturbance of a subjective nature."
I have always thought of 'croggle' as a verb, as in 'to croggle' somebody, i.e. to startle or stun them to the point of being gobsmacked, with the word 'croggled' better used to describe the resulting state of mind of the victim.
Silverberg later recalled that it was comprised of "crush" and "boggle", not "goggle."
|from Fancyclopedia 2 ca. 1959|
|(Grennell) Roughly meaning shocked into momentary physical or mental paralysis; a portmanteau-word, apparently, combining "crushed" and "goggled", and usually passive or reflexive in application.|