90秒で分かる「たくさん」はなぜ「沢」と「山」?

沢山(たくさん)って「いっぱいある」という意味ですが、なぜこんな漢字なんでしょう?沢山の語源を90秒でサクッと理解しちゃいましょう!
Learn Japanese vocabulary in 90 seconds - Theme: Date! Learn Japanese vocabulary in 90 seconds - Theme: Date!
90 seconds to learn Japanese vocabulary - Electric appliance! 90 seconds to learn Japanese vocabulary - Electric appliance!
Learn Japanese vocabulary in 90 seconds - Theme: Cooking! Learn Japanese vocabulary in 90 seconds - Theme: Cooking!