Steven M. Bellovin writes:

>Dave Korn's office is just down the hall from me -- if you want, I can 
>get an authoritative answer...  (For the record, even very early 

Hehe, well I don't think it's necessary to bother him, as long as
we can resolve the matter by reading the fine manual instead:

       echo [ arg ... ]
              When  the  first  arg  does not begin with a -, and
              none of the arguments contain a \, then echo prints
              each of its arguments separated by a space and ter-
              minated by a new-line.  Otherwise, the behavior  of
              echo  is  system  dependent  and  print  or  printf
              described below should be used.   See  echo(1)  for
              usage and description.

(notice the "system dependent" and reference to echo(1) in here.)

--mkb