1. Volume Ti-Tz of the OED does not contain the word "topos," nor does it appear under the entries for "humility" or "literary." (Ordinarily the OED can relied on to record just about every English word that has appeared in print prior to the 20th century.)
I have access to the full online version of the OED, which does contain the word topos. The earliest citation it has is to a 1948 work of Leo Spitzer, who was apparently a linguist and literary historian. Here is his Wikipedia page: http://en.wikipedia.org/wiki/Leo_Spitzer He was Austrian, and it seems quite possible that he could have read Curtius' treatise in the original German and begun to use the word "topos" himself in the same year. [For admin and other information see: http://www.mta.ca/~cat-dist/ ]