Very slow learner seems to have just learned this, maybe.

[Mark Kohut]

This appears in explicating Dylan's The Times They Are A-Changin'. Which I
sorta knew.

"The *a- <https://en.wiktionary.org/wiki/a-#Prefix_2>* in the song title is
an archaic intensifying prefix, as in the British songs "A-Hunting We Will
Go <https://en.wikipedia.org/wiki/A-Hunting_We_Will_Go>" and "Here We Come
a-Wassailing <https://en.wikipedia.org/wiki/Here_We_Come_A-wassailing>",
from the 18th and 19th century."

But never until now connected to Pynchon's witty jape: A--And.