(n.) a female fox
It’s not uncommon for male and female creatures to have often quite dissimilar names in English. Mare vs. stallion. Pen vs. cob. Bull vs. cow. And while a male fox is called a dog, a female is a vixen. Each one has its own reason for being, of course, but vixen is an especially interesting word etymologically, as it shows evidence of two particularly ancient processes in the early development of our language.
Despite appearances, vixen derives from fox. In Old English, a vixen was a fyxen. As the word, and our language, gradually changed over time, the initial “f” sound in fyxen changed into its voiced equivalent, “v”.
For the uninitiated, voicing is a phonological process in which the vocal cords vibrate slightly as a sound it produced. Some sounds have voiced and unvoiced, or ‘voiceless’, equivalents, meaning that their voicedness is the only thing that differentiates between their different forms. Pronounce a “f” sound and a “v” sound, for instance, and you’ll probably notice that they feel physically precisely the same, but sound noticeably different. The only difference between them is the slightly vibration of the vocal cords that accompanies a “v” sound. (If you can’t quite get your head around that, gently hold a finger on your throat while you say them and you should feel a slight buzz with the “v” that is absent on the “f”.)
So why did the F in fyxen become voiced? The best guess we have is that this change occurred in perhaps only one particularly resonant dialect of medieval England, but proved influential enough to catch on elsewhere. The change began in the 1400s, and had all but standardized across the country by the end of the sixteenth century. Other words changed too, of course—including the fane that you now find locked inside the word weathervane.
The other reason that vixen is an intriguing word is all to do with that ending, –en. That suffix was used for all manner of different reasons in Old English, including conjugating certain verbs, declining and pluralizing nouns, and forming diminutives. In some words, however, it was used to form specifically feminine nouns.
So a she-wolf in Old English was a wylfen. A she-bear was a byren. A goddess was a gyden. And a female fox was a fyxen. What makes that especially interesting, however, is that of this fairly scarce set of words, only vixen has survived in our language to this day.