This character is a combination of ⺊ a variant of divination (crack) and 鼎 round kettle (here simplified as 貝). Here 鼎/貝 is a phonetic element signaling the on’yomi, but also being used to express “request/seek.” Originally 貞 meant to “seek to learn the will of the gods by divination.” Its current meanings of “chastity” and “virtue” are thought by some to be a borrowed meaning. Others believe it to be an extended meaning, as in “acting in a manner approved of by the gods.”