If you’re noticing that you’re forgetting words you’re very familiar with, YOU ARE NOT ALONE!!
Really basic words are being lost in what people describe as a fog. The phenomenon is called "lethologica" and it’s due to stress. Stress releases cortisol and epinephrine which affects the brain’s ability to retrieve info like words.
If it’s freaking you out, play some brain games, like Sudoku, to exercise your mind. That will help get things back on track.
Source:Bustle