Think of something growing. The word is borrowed straight from Italian crescendo, which is the verb crescere, to grow, in its -ing form: growing, in progress, not finished. Put that on sound and you get volume climbing step by step. Put it on an event or a feeling and you get something gathering force over days. The one thing the word always insists on is the climb itself, which is why careful writers resist using it for the single loudest moment at the top.
Borrowed from Italian crescendo, the gerund of crescere, to grow or to increase. Italian has long supplied European musical terms, which is why this one arrived through music.
借自義大利文 crescendo，是動詞 crescere（生長、增加）的 gerund 形式。歐洲音樂術語長期使用義大利文，所以這個字是從音樂這條路進入英文的。
packet evidence: Wiktionary etymology for 'crescendo' (kaikki:3f6f69a190036ae4:493450445:12922)
From the picture
樂譜上的指示
同樣是「越來越大」，只是搬到紙上：譜上的 cresc. 或那個往右打開的角形，是在告訴演奏者把音量一路帶上去。看得見的記號，和聽得到的那一段，用的是同一個字。
noun · C2
In written music, the mark or word that tells players to get gradually louder, and also the passage that is played that way. The mark is a long narrow angle opening to the right, which players call a hairpin.
（樂譜上的）漸強記號
事情或情緒越來越強
把「正在長大」從聲音搬到別的東西上。活動、情緒、抱怨、期待都可以這樣長大，句型照抄聲音那一支：reach／build to a crescendo。
noun · C1
A steady build-up in an activity or a feeling, in which it gets stronger and stronger until it is at its strongest.
（活動、情緒的）逐漸高漲
noun · C1
A steady rise in sound, in which music or noise gets louder and louder until it is very loud. Many people also use the word for the loudest point that the rise ends at.
漸強；聲音一路變大的那一段