Not to worry I know how you feel. I tend to call people by the wrong name all the time. Even ones I've known for years.
What I have found and really appreciated in the dojo is that even when I am working with someone who ranks high above me they are all so patient and willing to work down to my level and help me learn.
I'm really kinesthetic and its hard for me to grasp a movement until I have felt it correctly, so sometimes it can seem like I'm never gonna figure it out. Seeing it demonstrated does not do nearly as much for me as feeling it does. The cool thing is every one of my fellow Aikidoka is right behind me wanting me to succeed and never makes me feel bad. Actually I have found that only I can make me feel silly or stupid. So I laugh at myself and keep going. It eventually will come clear when it is time.
Don't let fear of looking silly slow you down. Everyone had to begin at the beginning just like us and you will find that they remember how it felt.