Yup, I agree. And I split it in two posts aiming to avoid confusion in the learner head.
      First the A-frame, even providing images of it, "A picture is worth a thousand words"; anyway your point was very useful and come in handy.

      Then comes the a- verbing.  The author may have chosen this wording because the verbs coming after the a- are often ended in ''ing".
      Perhaps the fact of being spoken in the country (área rural/campo) confirms that

A-verbing  it is "something that has survived from the past; "a " is a holdover from earlier varieties of English, but it is familiar to modern readers from nursery rhymes and folk songs, both old and modern . . .

      That is, it is a remnant/vestige/residue/remainder of the old English, in the sense of earlier English talked in the states (and the U.K.) at the time. 

      I equally deemed interesting the  following piece of text, kinda informative:  

: "Wolfram and Fasold (1974), who studied the use of a-verbing in Appalachian English in West Virginia, say that the prefixed -a emphasizes the duration of an action. 'She's working' means that she's engaged in a relatively short-term task. 'She's a-working' means that the task is of longer duration. . . . Feagin (1979) [found that] a-verbing was used to intensify the action or to create dramatic vividness. She found that a-verbing forms were common in stories about ghosts, accidents, murders, tornadoes, and other dramatic topics."

      I don´t know much about etimology, but perhaps ''asea/ashore'' might come from structures like that? I really don´t know for certain...but it may be one possibility.

      Indeed, this was an inteligent question from the (very) scratch!