Adolf Deissmann (1866-1937), Light from the Ancient East
, tr. Lionel R.M. Strachan (New York: Hodder and Stoughton, 1910), p. 69:
As a matter of fact words are constantly turning up in the newly discovered texts which one may seek in vain in the dictionaries. It is equally natural that many words can only be found a few times, sometimes only once, in the whole body of the texts known to us. Nobody with common sense will suppose that these were all coined by the writers on the spur of the moment: they are little discoveries for the lexicographer, it is true, but not inventions by the authors.3
3 In Greek phrase I should say that they are ἅπαξ εὑρημένα, not ἅπαξ εἰρημένα.
I.e. found only once, not uttered only once.