A useful way to hold this word is the laurel crown at the end of a course of study. Somebody has worked for years; now there is a moment where the work is closed off and marked. All three uses sit on that moment, and they differ only in what is handed over at it — a set of exam results, a degree, or a speech and a quiet evening before the certificates arrive. The word is long and formal because the moment it names is a formal one.
The supplied source says the word came into English in 1625 from French baccalauréat, from Medieval Latin baccalaureus, itself an altered spelling of baccalarius (a young man aspiring to knighthood, an apprentice) reshaped to look like bacca lauri, laurel berry, the ancient sign of victory. That deliberate reshaping is where the crown picture comes from, and the same root gives English bachelor.
packet 附的來源說這個字 1625 年進入英文，來自法文 baccalauréat，再往前是中世紀拉丁文 baccalaureus。那個拼法其實是把 baccalarius（見習的年輕人）改寫成看起來像 bacca lauri，也就是古代象徵勝利的月桂果。冠的畫面就是從這次刻意的改寫來的，而同一條線也長出了英文的 bachelor。
Wiktionary entry for 'baccalaureate' as supplied in this packet (source_ref kaikki:3f6f69a190036ae4:686561229): 'First attested in 1625; borrowed from French baccalauréat, from Medieval Latin baccalaureus, an alteration made to baccalarius ... for it to resemble bacca lauri (laurel berry)'.
Two branches
結算學業的那張資格
這一支是冠本身：你走完了，這是給你的那張紙。差別只在走完的是高中還是大學。
noun · C1
An examination covering several subjects that students take in their final year of school in France and some other countries, and in international schools. Passing it is what lets them apply to university.
高中畢業會考
戴冠之前的那場道別
還是同一個時刻，但鏡頭往前挪了一兩天，停在還沒發證書、大家先安靜坐下來聽一段話的那個晚上。
noun · C2
In the United States, a service held for a graduating class shortly before graduation, in which a speaker gives a farewell address in the form of a sermon.
畢業前的祝福禮