A, in composition, seems to have sometimes the power of the French a in these phrases, a droit, a gauche, &c. and sometimes to be contracted from at; as, aside, aslope, afoot, asleep, athirst, aware.
If this, which he avouches, does appear,
There is no flying hence, nor tarrying here.
I gin to be a weary of the fun;
And with the state of the world were now undone. Shakespeare's Macbeth.
And now a breeze from shore began to blow,
The sailors ship their oars, and cease to row;
Then hoist their yards a-trip, and all their fails
Let fall, to court the wind, and catch the gales. Dryden's Ceyx and Alcyone.
A is sometimes redundant; as, arise, arouse, awake; the same with rise, rouse, wake.