noxious

This word is prohibitive off the top: no, x. The ox could be an emoticon for a skull and crossbones. Given the sense of the word, the x in the heart is not catchy as in extra or maximum or functional as in fixing; the o and o stare back at you like a baleful glare – or the lights on a railroad crossing marked by the x (the i may be the post, the signal arm, or the person tied to the tracks). This word has unpleasant echoes, such as toxic and Nixon. It keeps bad company, too: common nouns it modifies include fumes, weeds, odors, chemicals, gases, emissions – is one of these words not like the others? Note how this word, which came to us from Latin noxa “harm”, has taken on an almost exclusively gaseous air (I cannot say whether the steam-hissing sound of the second syllable had any influence on this narrowing), with the exception of the more technical use with weeds. Add the obstacular ob to the front, on the other hand, and you get a word mainly applied to persons: obnoxious, which tends to modify behaviour and often to be preceded by rude and or loud and. And yet obnoxious has another sense, a bit older but now largely disused: “exposed or subject to something, especially to something harmful.” In this sense, a person who is obnoxious may be the victim – and quite innocent, perhaps ironically, given that the noc in innocent comes from the same root as noxa, the heart of obnoxious.