Most villains call Sam, Sammy for psychological reason. They do it to create a feeling of smallness and inadequacy.
Sam although very self-reliant he tends to fall back as most people do when they reunite with family into their family roles. Sam being the youngest in the family has always had to follow directions most of the time begrudgingly ( ). Because of that being called, Sammy by villains puts him in two different mindsets:
1) Small: So when villains called him Sammy it remind him of that time of the time when he didn’t have control of his life but wanted it, but also puts him in the place where he needs to have approval and reassurance for his actions. Most of the time that resulted in Dean having the last word and Sam being upset about it but following along (before season 4).
*Ruby: she used his feeling of smallest to control Sam, she knew how much he wanted freedom and control and she gave it to him. She gave him freedom to have control over something in a set of boundaries she created. She took a page right out of “bringing up bebe” by Pamela Druckerman. All the while she was putting him in a position where he seeks her approval and no longer Dean’s. Ruby got Sam addicted to demon blood by reassuring him to do the wrong thing, since Sam got the feeling of freedom, he never questioned it. Ruby was an evil mastermind instead of a very effective parent like the French. I personally think Sam would have thrived in a French kind of parenting style (if you want to know why )
2) Inadequate: Sam has always been very smart and self-reliant so when he was a child he thought he had all the answers even when he didn’t have them. I’m sure Sam as well as all children made mistakes because they don’t know everything they are just learning thus feeling inadequate. How many kids have said “I can never do anything…I’m always too small or too young for something” if you are the youngest sibling is possible you were the one saying those things. This feeling is hard enough for kids how are not as smart, independent and self-reliant, well it’s twice as hard for Sam.
*Lucifer: When he was in Sam’s head, he used it to make Sam feel weak, unsure and insecure (and of course, the sleep deprivation didn’t help either)
Other villains have also used Sammy to irritate him as is childish, but the truly smart/conniving evil ones didn’t take that on just for fun.
Dean’s “Sammy”: Dean was a mother, a father and brother more adequately he was a “frother” (like Tim Allen said in Home Improvement)
· The brother in him calls him Sammy to piss him off
· The mother and father in him calls him Sammy to comfort him, to have him obey and to just plain love him like parents do.
For Dean drawing the line between all this roles has been hard but he made a step in the right direction after the Ruby incident. Dean then continue to grow and learn to do perhaps the most import and hardest thing a parent has to do “letting go”. It was in last season’s episode where his parent role encourage his son to take the lead.
For Sam, Dean’s “Sammy” is:
I got you, I love you, I’m going to mess with you but you know I love you ,nothing bad is ever going to happen when you are with me. He likes it because of that
For Sam all other “Sammy” :
Are no long effective because he grew into his own person and is now in a happy place
John's Sammy is just like Dean's parental Sammy. Although people don't recognize he was affectionate and called his kids buddy and kiddo. He never called them stupid or idiots because good parents don't do that