idiomaticityn.

1887 W. C. Wilkinson Classic German Course ii. 35 The indescribably telling prose in which Luther writes, with its homeliness, its idiomaticity, its nervousness, its directness, its pith, its point, its bite, suffers cruelly in any possible English translation.

1964 Internat. Jrnl. Amer. Linguistics 30 409/1 For greater order in lexicology, I think, there exist at least the rudiments of a theory based on such concepts as ambiguity, contextual disambiguation, idiomaticity, depletion, and the like.

1998 Word 49 14 Item (64) has acquired the status of idiomaticity and it is questionable whether there is in fact a congruent version to sit in the back except where one is speaking literally with respect to a vehicle.