It's entirely another to read in his memoirs that they were indeed wedding robes, sent by Feisal's Circassian great aunt from Mecca as a hint that Feisal should be thinking about marriage.
And that Feisal suggested that it would stop people from constantly asking why Lawrence was visiting him in his tent.
As Lia and I independently noted, it gives "Gee I wish I had a dress like that" a WHOLE NEW MEANING.
I should fix this because I know by now it's actually not a burnoose. Keffiyeh, agal, bisht, dishdasha. (And I kind of love saying dishdasha.)