wild onions or leeks
韯 refers to wild onions or leeks, a specific plant. The meaning is narrow and concrete, with no clear abstract extensions.
韯 is a rare character. It likely combines 韭 (leek) with a phonetic element on the top-left, but the exact historical development is uncertain.
The bottom part 韭 looks like a bundle of long, thin leaves, like wild onions or leeks growing upright. The top part adds a sense of something wild or scattered.
For セン, picture a thousand (千, せん) wild leeks growing on a hillside: 千 -> セン, and the hillside is covered with 韯.