Most countries land borders are somewhat rounded, and it's easy to guess why - it's eazy to defend a rounded shape, and it's hard to defend "bulges" because it can be easily surrounded and occupied.
However, Jordan's map has a characteristic nearly rectangular "bulge" between Syria and Saudi Arabia, as can be seen on google maps here
The lines are straight, so you can understand that there were no valuable points to either of the sides. Also, you can't see any town on Goggle maps at this territory, only desert.
So why this territory was allotted to Jordan and not to, say, Syria or Saudi Arabia?