portentous

At the heart of portentous is portent, a word for an omen or sign, which comes to us from the Latin noun portentum of the same meaning. And indeed, the first uses of portentous did refer to omens. The second sense of portentous, describing that which is extremely impressive, developed in the 16th century. A third definition—"grave, solemn, significant"—was then added to the second edition of Webster's New International Dictionary in 1934. The word's connotations, however, have since moved into less estimable territory. It now frequently describes both the pompous and the excessive.