My Grandmother used to do the same thing! She always said that the devil was sittin' on her shoulder and she was throwing salt in his eyes!

1) "What is the origin off throwing salt over your shoulder for good luck? It refers to Lott's wife who looked back yearningly on Sodom when being led to a more moral place and was turned into a pillar of salt by a wrathful God. You must put the devil behind you or risk the same consequence. Paul Roberts, Lake Cathie. Superstitions about salt date back to biblical times when salt was a highly prized commodity as it was crucial in preserving food, even used in lieu of currency. So spilling salt was considered an almost sacrilegious offence and throwing salt over your shoulder at such a moment was, like blessing someone after they've sneezed, aimed to "keep the devil at bay". Depending on your interpretation, the salt is either intended to blind the devil so he can't witness your error, or keep him from sneaking up on you while you're cleaning up your mess. It's important to note that the superstition calls for the offender to throw salt over the left (or "sinistra" - sinister) shoulder ie the devil's side with your right hand (your "good" side). John Moir, Mollymook In biblical times, salt was an expensive commodity. Spilling salt was almost a sacrilegious offence. The offender would throw salt over his/her left shoulder to ward off the devil . Michelle Berkowitz, Woollahra It dates back to when people were scared of getting a-salted Jen Lynch Camperdown Google tells of the superstitions of salt and the devil on your left shoulder, but is there evidence that salt, being valuable and often expensive, became a throwaway item at the encouragement of the salt production and distribution industry? J. Barrie Brown. Gordon. If you threw pepper over your shoulder , you'd sneeze Jen Lynch, camperdown" Source: http://www.smh.com.au/news/big-questions/what-is-the-origin-off-throwing-salt-over-your-shoulder-for-goodluck/2006/08/24/1156012662267.html?page=4 2) "Lots of superstitious people, when they spill salt, will take a pinch of it in their right hand and throw it backwards over their left shoulder. My grandma does it. I do it too, but not out of superstition, more out of lack of any other meaningful culture. Superstition has it that, at all times, a devil (or perhaps the devil) waits over your left shoulder, and also that spilling salt is bad luck (perhaps because it used to be rare and precious). Hence, you can mitigate your bad luck by throwing salt into the eyes of the devil. There's also a belief that your guardian angel (who can be found over your right shoulder) spills salt to warn you of evil nearby. Either you throw the salt to hurt the devil or, as salt was valuable, as an offering to placate him. Like lots of other superstitions in a Christianised culture, it has a Christianised explanation: spilling salt is bad luck, because Judas spilled salt at the Last Supper. This is somewhat equivalent to the Christianised explanation for not sitting down thirteen at the table, and almost certainly a red herring." Source: http://everything2.com/index.pl?node_id=944543&lastnode_id=0 3) "The Devil, or evil spirits, will be lurking behind you on the left side. Salt is sacred and wards off evil. If you spill salt, you've desecrated something holy, and you must pick it up with your 'good' hand (right) and throw it over your left shoulder to blind the Devil/evil spirits so that they cannot take the opportunity to do you harm." Source: http://www.surlalunefairytales.com/boardarchives/2003/apr2003/saltshoulder.html 4) "Evil spirits lurk over the left shoulder - throw salt over this shoulder to ward them off. In Roman times, salt was a very valuable commodity, giving rise to the word "salary" and was considered a form of money at the time. If salt was spilled, that was considered very bad luck, that could only be avoided by throwing some of the spilled salt over your left shoulder to placate the devil." Source: http://www.anythingleft-handed.co.uk/lefty_myths.html

The person behind her was an unsavoury character????

Salt over the shoulder The Devil, or evil spirits, will be lurking behind you on the left side. Salt is sacred and wards off evil. If you spill salt, you've desecrated something holy, and you must pick it up with your 'good' hand (right) and throw it over your left shoulder to blind the Devil/evil spirits so that they cannot take the opportunity to do you harm.

to ward off evil spirits its done alot in ireland as well

In most cultures and beliefs salt was said to ward off unpure things such as vengeful spirits and demons because salt itself is pure. When you throw it over your shoulder it's suppose to keep those things away.

My family always does it when someone knocks over the salt shaker if salt is spilled we throw it over our right shoulder (we've actually had salt fights lol) ...idk why though I just thought it was like walking under a ladder.