Is the origin of "open sesame", "open says me"?

No. It’s from the story “Ali Baba and the Forty Thieves,” from Tales of the Arabian Nights, or the Thousand and One Nights, a collection of Middle Eastern folktales linked together by the story of Scheherazade, the storyteller. They have been retold and used in all kinds of ways.

That story is one of the best-known of the collection. A gang of forty thieves keeps their treasure in a cave guarded by a secret password, namely, “Open sesame.” (The original tale is in Arabic.) Ali Baba finds it out and tries to rob the thieves. Bad idea.

Yes, since the original tale starred a moustachioed Italian plumber.

It about a group of sesame seeds who we open sexually.

Ali Baba originally hired a sorcerer to enchant the cave. The sorcerer asked Ali what he wanted the password to be. Ali first asked the sorcerer if he was going to have to change the password every 90 days or so, like all the ridiculous cyber nuts wanted him to do. The sorcerer pointed out to him that computers had not been invented yet so there was no cyber crime. He could leave the password alone.

Ali, not being a particularly creative guy thought he’d try to make it something he liked a lot. At first he thought of “Bouza” (Egyptian beer) because he really liked that! But then he realized he could show up drunk some time and yell for more bouza and the damned cave would just open up. He also was fond of poppy seed pita. He thought that making it “Poppy” would be good, but then thought that anyone that knew him might guess it. Then he remembered the vendor that was selling tasty goat burgers he called the Big Zayd. It was two goat patties with a secret sauce, pickles, kale, goat cheese served in a sesame seed pita. He would fool everyone by using “sesame” as the password!

The sorcerer, after being bored having waited so long for Ali to rev up his non-existent imagination, set the password into the spell for the cave. Ali thanked him, gave him the gold he wanted as a fee, and then cut his head off. He didn’t want the sorcerer to come back some time and use the password. He wasn’t worried about his band of thieves as they had even less imagination than he did and he knew they couldn’t think up a plan that included using the password for themselves.

It is either that or it could have come from the Hebrew word “Sisma” (pronounced Sees-ma”