Aww sweetie it's probably age, i had my grandpa (RIP my funny and wonderful grandpa) till he was 96 and he'd often spell or say my name incorrectly (well it is hard here in OZ they're all used to Glenys not me GLYNIS). At first i used to be you know kinda not be happy then i finally realised that hey, he loved me and i was still on his mind no matter what.
Should you find out if he's OK?