LotR -- Book 5 - Chapter 02 - The Passing of the Grey Company

[Lalwendë]

Something odd which may explain an earlier part of LotR struck me in this chapter. When the Dunedain are riding up this is the description:

The pursuers brought their steeds to a sudden stand. A silence followed; and then in the moonlight, a horseman could be seen dismounting and walking slowly forward. His hand showed white as he held it up, palm outward, in token of peace; but the king's men gripped their weapons. At ten paces the man stopped. He was tall, a dark standing shadow. Then his clear voice rang out.

Then Merry has the following thoughts:

Merry breathed a sigh of relief. He had thought that this was some last trick of Saruman's, to waylay the king while he had only a few men about him

To me it is clear that the upheld, white hand must be some sign of peace in Middle Earth, certainly amongst the Dunedain, and as likely as not a universal sign amongst Men, or else it would not have been given. Yet the sign is viewed with suspicion and immediately I thought of Saruman's 'white hand' symbol. This is then backed up by the fear that Merry felt, as he associates the symbol with Saruman himself.

There was discussion about what Saruman's white hand symbol might mean, and this has made me think that perhaps Saruman made use of pre-existing gesture of friendship and peace in order to create his own symbol. His symbol was made in mockery of the sign for peace between Men, or did he utilise it at first to win their confidence and trust?