This is an image, not an idiom. It's a figurative way of describing how we store information in our brains. This is the image: If you don't have any storage hooks in your house, all your coats and hats and so on will be in an untidy pile somewhere. They are all in a mess, and it's impossible to find the things you need. A much better idea is to get a hammer and bang some storage hooks into the wall. That way, you can store your things neatly and in an organised way, and they'll be easy to find when you need them. Memory works in the same way. We build frameworks inside our brains to store and then later retrieve information in a systematic manner. Let's say, for example, that when you learnt English, you had to internalise the concept of countable and uncountable nouns. Thanks to your English studies, there are now some 'hooks' in your brain on which you can 'hang' countable and uncountable nouns. This means that when you go on to study Italian, the 'hooks' for remembering the equivalent Italian grammar are already there. The mental framework for your Italian studies have already been laid down by your English studies. The vocabulary might be new to you, but the concepts are familiar. I hope that makes sense.

I'm British and have never heard this one before either. It could mean that the more you study different types of languages, the easier it gets to remember what you've learned and the easier it is to learn other languages in the future. It expands your capacity to store language based information.

I took this to mean that the more languages you learn, the easier it is to learn new languages. I have never heard this idiom before, though.

This idiom is totally unfamiliar to me. Sounds British or Australian, or an older American idiom I’m not familiar with. But guessing by the context it just means each language adds a little more to your life. A little more support that you can rely on. Professional Teacher www.italki.com/teacherhelpme

The prior sentence: "I was also a standout at reproducing sounds," he continued. "But... (this is about a gift for languages)