Yes, that's right, I is for arm. In Semitic, the letter may have originated in a hieroglyph for an arm but was later reassigned to /j/ (as in English "yes") by Semites, because their word for "arm" began with that sound. Why-i!
Don't forget to grab the editable eps and use the character for your project, or smash it up and send me a copy back. The edit's I'll feature here as a changelog to track its development.