Why are swap rates tripled on Wednesdays?
If a position is held overnight on a Wednesday (to Thursday), the normal swap rate is tripled. This is because spot forex trades have a 2-day settlement period; an FX trade closed on Monday settles on Wednesday, a trade closed on Tuesday settles on Thursday, etc.
Keep in mind that markets aren’t open on weekends, but trades can still be held over this period. By charging triple swaps on a Wednesday, this effectively accounts for holding trades over the weekend.