a- -ing

Etymology
The first element is a reduced form of ; the second element is the gerund suffix  from,. Therefore, I go a-hunting = I go on (a) hunting/I go on a hunt. Due to confusion with the unrelated present participle ending -inge (alteration of -inde from, the use of a(n) preposition (which was fast evolving into a distinct prefix) was extended to present participles (and not merely restricted to preceding verbal nouns). With this development, the a- -ing circumfix emerged. Nowadays, in the few dialects of English (such as, notably the dialect of Smith Island, Virginia) which retain this circumfix, it is only circumfixed to words which function as part of a verb phrase; otherwise, -ing is suffixed.

Usage notes

 * The common practice is to hyphenate this circumfix’s first element and the word it inflects (e.g.: “a-running”); unhyphenated spellings (e.g.: “abreaking”) are rarer, but nonetheless correct.