Abarim Publications' online Biblical Hebrew Dictionary
There are two separate roots of the form חלד (hld) in the Bible, and they obviously have nothing to do with each other:
The root חלד (hld I) is the assumed root of the masculine noun חלד (heled), a curious word referring to the duration of life (Job 11:17, Isaiah 38:11, Psalm 89:47). As such it is sometimes translated with the word world, but in the sense of the world as "the total scene of life and action on the earth" (as HAW Theological Wordbook of the Old Testament puts it - Psalm 49:1, Psalm 17:4).
The root חלד (hld II) is unused but in late Hebrew it's used to mean to dig or hollow out. In Aramaic this verb means to creep or crawl. The derived masculine noun חלד (holed), meaning mole or denoting some kind of rat or burrowing animal, is used only once in the Bible, in Leviticus 11:29, where a holed is listed among the unclean animals that swarm.