inset (n.)youdaoicibaDictYouDict[inset 词源字典]
1550s, "influx of water, place where water flows in," from in + set (n.2). Meaning "extra pages of a book, etc." is from 1875; that of "small map in the border of a larger one" is from 1881.[inset etymology, inset origin, 英语词源]