My thoughts exactly:
the larger the library you have in your head, the longer it usually takes to find a particular word (or pair).
Scientists who study thinking and memory often make a broad distinction between “fluid” and “crystallized” intelligence. The former includes short-term memory, like holding a phone number in mind, analytical reasoning, and the ability to tune out distractions, like ambient conversation. The latter is accumulated knowledge, vocabulary and expertise.
I know this is true because my skills as a web-master are very fluid. They flow out of my memory way too fast as I try to figure out what I am doing with my website and setting up a newsletter but recipes which entered long term storage years ago never fail me and everyone thinks I am an intuitive cook.