Think of running your finger up the side of something and asking where it stops. That stopping point is the rise. On a building it stops after a few floors; on a pair of trousers it stops at the hips. Low-rise is the answer 'not very far up'.
From the word’s history
The source records the building use as a retronym: the word was made later, as an opposite to high-rise. The clothing use is listed under a separate etymology, described as referring to the low waistline.
字典把建築的用法記成一個「回頭造的詞」：先有了 high-rise（高樓）這個說法，才反過來替原本那些不高的樓取名。服裝的用法則另外列在一條來歷底下，說明它指的是較低的腰線。所以這兩個意思在字典裡是分開記的，上面那個「往上到哪裡」的畫面只是幫你一起記住，不是在說它們同源。
Wiktionary via packet: kaikki:3f6f69a190036ae4:1193208377 — '(architecture): A retronym created as an antonym to high-rise'; kaikki:3f6f69a190036ae4:1193210243 — 'Referring to the low waistline.'
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