I have always found the a- prefix to words (as in anew, ajar, aside, awake, afoot, a-hunting, etc.) fascinating. The NOAD says on this topic:
a- 2. prefix
•to; toward : aside | ashore.
• in a specified state or manner : asleep | aloud.
• in the process of (an activity) : a-hunting.
• on : afoot.
• in : nowadays.
ORIGIN Old English , unstressed form of on.
a- 4. prefix
1 of: anew.
[ORIGIN: unstressed form of of ]
2 utterly: abash. [ORIGIN: from Anglo-Norman French (corresponding to Old French e-, es-), from Latin ex.]
While this gives quite a few examples, it leaves some areas of doubt to me:
- At what time did this phenomenon happen?
- It seem quite restricted to words of Saxon origin, as I don't see it used with words of Romance languages. Is that a consequence of point 1, or is it because usage wouldn't aggregate an Old English prefix with, e.g., a word of French origin?
- Were there others words formed which haven't endured?
- Arguably subjective: I wonder how it came to pass that the same prefix is used with so many different meanings.