An earlier post, “The Supersession of Literal Meaning (incredibly, unbelievably),” provided a possible motivation for the rise of the two adverbs at the expense of the traditional emphatics very and extremely. But in view of the clear fading of the latter two under the onslaught of the longer words, length ought now to be considered as a possible driver of the change, even though the tendency toward hypertrophy that has been instanced repeatedly in earlier posts cannot be ruled out as a contributory factor.

The length of a word can enhance the word’s suitability as an emphatic because by comparison with shorter candidates like very and extremely a pentasyllable and a quadrisyllable like unbelievably and incredibly, respectively, enhance the iconic relation between sound and meaning that is the teleological end-point of all linguistic change. Here, emphasis as a meaning is abetted in the measure that the formal means of its expression promotes this iconicity, the relative length of words clearly being one such means.