ma.her sha.lal chash baz is used as a proper name written on a tablet and given to a son.

The attested form functions as a proper name: it is written on a large tablet in Isaiah 8:1 and then assigned as the name of a newborn son in Isaiah 8:3.

1. Proper name in a written and naming context · dominant

   The form is tagged Noun · Proper in both occurrences. In Isaiah 8:1 the APB renders the instruction to write “Maher-shalal-hash-baz” on a large tablet; in Isaiah 8:3 it renders the command, “Call his name Maher-shalal-hash-baz,” after the prophetess bears a son.

   Isaiah 8:1Isaiah 8:3

In the Anselm Project Bible: The APB presents the term unchanged as “Maher-shalal-hash-baz” in both verses: first as writing on a tablet, then as the son's name. The verse is read as a whole.