It’s hard to remember this kanji by the origin.
However, I will think of a way to help you.
線 = 糸 + 泉, 糸 means “thread” and 泉 means “spring”.
So you can remember this kanji by The spring is just like many threads/lines.
So 線 means “line”.(Below is the origin and development of the kanji 泉, which is the main part of 線)