You can start with one plant: a small evergreen tree with stiff, shiny, very dark leaves that stay on through the winter and smell strong when you rub them. Because those leaves bend without breaking and never lose their colour, they can be woven into a ring and set on a person's head, and a ring of leaves worn that way has long been a way of showing that this is the one who won. From there the word stops being about a plant at all: the crown you can see comes to stand for the honour you cannot, and then for the whole pile of praise a success brings. Once the honour is something you own, English asks the obvious next question — what do you do with it? Lie down on it, or guard it?
From the word’s history
Wiktionary gives laurel as inherited from Middle English laurer/laurel, from Anglo-Norman lorer, from Old French lorier, from Vulgar Latin *laurarius, from Latin laurus, 'laurel'. So the chain runs back to the name of the plant itself; the honour meanings are later growth in English, not part of the root.
詞源資料寫的是：中古英語 laurer／laurel，來自盎格魯-諾曼語 lorer，再上去是古法文 lorier、通俗拉丁文 *laurarius，最後是拉丁文 laurus，意思就是「月桂」。所以這條線從頭到尾都是那棵樹的名字。「榮譽」那幾層是後來在英語裡長出來的，不在字根裡。這裡要分清楚：把葉環和榮譽連起來是一個好用的想法，但那不是這個字的來源。
Wiktionary, entry 'laurel' (noun), etymology field supplied in packet; source_ref kaikki:3f6f69a190036ae4:320402965
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