Broadcast originally called The Sound of Hackney? (5)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

I’m not sure I fully understand the nuance of this one. A hackney can be a horse, as well as a carriage or the part of London, and horses neigh, but is there more to it? EDIT see below comment, it sounds like née  = originally called. Thanks jackkt.