Chinese olive tree
欖 refers specifically to the Chinese olive tree, a plant known for its fruit. The meaning is narrow and botanical, without broader abstract extensions.
欖 combines 木 (tree) with 覽, which likely contributes the sound ラン. The character was created to name the Chinese olive tree specifically.
The tree radical 木 beside 覽 suggests a specific tree. Picture a Chinese olive tree with branches so wide you can 覽 (look over) the whole orchard from its shade.
For ラン, imagine running through an orchard of Chinese olive trees: run -> ラン, and the trees stretch in long rows.
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Chinese white olive (Canarium album)