Clipping nails out of order
When my informant was a child he can remember his mother telling him that clipping his nails in order was bad luck. If one clipped the first three in order one should switch the order for the last two in order not to cause bad luck. This applies to both fingernails and toenails. He says that while the only practices it occasionally, if it does occur to him while trimming he does take care to go out of order.
He told me that his mother learned it from her mother and he supposes that it was passed down like that for some time as he has no knowledge of where that superstition started. He also says that while he does not practice it every time, it is something he would pass on to his children if he has any. So while the reason for the tradition is lost it still lives on in those who learn if from family.
The fact that he only does it sometimes proves that the reason he would trim them out of order isn’t to avoid back luck its to comply with something he was taught by his mother. For him it has become more of a tradition that something seriously done to avoid bad luck. There is nothing else that my informant told me that would make this practice stand out as more than just another practice to avoid bad luck.