Who were the men refusing the call of Gondor?

[Legate of Amon Lanc]

What Boromir says exactly is:

But still we fight on, holding all the west shores of Anduin; and those who
shelter behind us give us praise, if ever they hear our name: much praise but
little help. Only from Rohan now will any men ride to us when we call.

Which is really interesting, this would suggest someone Boromir really knows and someone who "shelters behind Gondor". Perhaps he might be referring to his recent journey, maybe he was speaking with some men from the wilderness around Tharbad - if they have any knowledge of Gondor - but there could be some remaining tales about the times when Tharbad was held by Gondorians (before 2912 TA)... But I'm not sure: these folks have problems of their own and I think they wouldn't give the Gondorians praise any more than the Breelanders. Or maybe there were some non-Gondorian Men similar to the Oathbreakers hiding on Andrast?

I think the sentence "Only from Rohan now will any men ride to us when we call" does not necessarily mean that Boromir remembers "testing" this call: he might just refer to his political, geographical, historical etc. knowledge. To anyone who looks at the map of M-E it is pretty obvious that at this time there is no realm except of Rohan from where anyone could come to Gondor's aid.