a man's pen = the carving tool of the people. The writing was to be legible, in the language of the common people (not in the language of the priests or educated classes). Eastern languages have these two, down to the present day. Compare Hab_2:2. "Pen" is put by Figure of speech Metonymy, for the writing written by it.
man's = a common man's. Hebrew. 'enosh. concerning = "for Maher, &c. "
Maher-shalal-hash-baz = haste, spoil, speed, prey. (Note the Alternation.) These words are explained in Isa_8:4, and may be connected thus: he hasteneth [to take the] spoil, he speeds [to seize] the prey. This child was a sign, as also the child in Isa_7:14.