A colloquial, dialectal or old-fashioned way of speaking.

It could also mean that the subject has more incentive to do the action, according to sources.
(French guy here, if So wants to fix my writing)
If I hadn't a-been here...

The times they are a-changing

I told her I (had?) bought croissants and she came a-running

.A-verb-ing/ed.
by Totocar February 15, 2018
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