a searching out: the probing of a matter to get to the bottom of it, or the hidden bottom such probing is trying to reach
This is the noun that belongs to the verb for searching something out (חקר). It does not describe a person searching; it names the search itself. All twelve of its appearances are in poetry, and seven of them are in Job.
A noun like this can face two ways. It can name the activity and its findings: what an earlier generation looked into and learned, or the churning of a group that cannot make up its mind. It can also slide across to name what the activity is reaching for, the far bottom of a thing. When Job is asked whether he has walked in the recesses of the deep, "recesses" is this word: the part of the sea that a search would have to get down to.
That second move is what made the word famous. Six of the twelve uses, and probably a seventh, are a flat denial, "there is no searching out of it," which is this language's way of saying that a subject has no floor for a searcher to reach. It is said of:
- the great things God does, which nobody can trace to the end
- the greatness of the LORD himself
- his understanding, which never tires and never runs short
- the sheer number of his years
- and once, drily, the mind of a king
English almost always folds that whole phrase into one adjective, "unsearchable" or "unfathomable," so the noun vanishes from the translation even though it is what drives the sentence.