Under this head I will introduce a few observations on the use of a. Grammarians have supposed that a, in the phrases a going, a hunting, is a corruption of the preposition on; a supposition, which, if we attend to the sense of the phrases, appears highly absurd, but which etymology, in a great measure, overthrows.
In the first place, the preposition is not among the original parts of language; its use, and consequently its formation, are not necessary among rude nations; it is a part of speech of a late date in the progress of language, and is itself a derivative from other words. I have, in another place,[102] given some reasons to prove on to be an abbreviation of the numeral one, or top one. It is very evident that on is a contraction of upon, which was formerly written uppone; and there are good reasons for believing the latter to be derived from top one. In addition to the authorities quoted in the Institute, an example or two from Chaucer will almost place the question beyond a doubt.
"There lith on—up myn hed."
Cant. Tales, 4288.
That is, there lieth one upon my head; where up is used for upon, as it is in other places.
"No more, up paine of losing of your hed."
Ibm. 1709.
That is, upon pain of losing your head.
The word up is undoubtedly but a corruption of top, or a noun derived from the same root, and this hypothesis is supported by the true theory of language; which is, that rude nations converse mostly by names. Up myn hed, is top mine head. An improvement of this phrase would be the use of one, ane or an, to ascertain particular things; uppone, upon. In the progress of language, these words would be contracted into on, which we denominate a preposition.
I am very sensible that Chaucer used on in the manner mentioned by Lowth; on live for alive; on hunting; on hawking; which would seem to warrant the supposition of that writer, that a is a contraction of on, considering on originally as a preposition. But it is contrary to all just ideas of language to allow such a primitive part of speech. On the other hand, Chaucer uses on for other purposes, which cannot be explained on Lowth's hypothesis.