Tang Rhymes (Tangyun) and Collected Rhymes (Jiyun) state the pronunciation as ni. It is pronounced similarly to nian. Explaining Characters and Writing (Shuowen Jiezi) defines it as the act of taking items privately and hiding them. The character structure consists of an enclosure (wei) and a right hand (you).
Additionally, Tang Rhymes (Tangyun) states the pronunciation as nian, and Collected Rhymes (Jiyun) states the pronunciation as nie. The meaning is the same. Sometimes it is also written in a variant form (nan).