Nice idea, Mithadan, but as WCH has already pointed out, osanwe kenta was "direct thought transference" and Merry felt the blade in his heart and not just remembered it.
Also, I thought that the ability had atrophied down the years--ages--once language had developed and that by the Third Age only very few had the ability. We are told how Melkor was able to instill his thought, but was osanwe possible with unconscious minds?
Further, it seems a bit of a canonical conundrum to point to an essay Tolkien wrote c. 1959 when the Barrow Downs chapter was written in 1938, between Lost Roads (1936) and the Notion Club papers (1945-46). I think WCH has already said this.
Mithalwen, I think it is interesting that Merry's explanation at Bree concerns being overwhelmed by deep waters.