One doesn’t pronounce יהוה, but with so many titles to be found in the Tenach for referring to יהוה, why would we refer to Him as ‘HaShem’ then? Why not stick with Adonai, Anochi, El Shadai etc. like our forefathers did? (Or in case you want to refer to it more directly use Yud-Hey-Vav-Hey?)
What I would like to know is how and when people came up to use the title ‘HaShem’, who came up with it or what is the oldest source known to us teaching us the usage of ‘HaShem’ as a reference to יהוה?