Unsearchable - Vine's Expository Dictionary of New Testament Words
Unsearchable[ 1,,G419,anexeraunetos / anexereunetos ] a, negative, n, euphonic, ex (ek), out," eraunao, "to search, examine," is used in Romans 11:33, of the judgments of God.
[ 2,,G421, anexichniastos ]
with the same prefixes as in No. 1, and an adjectival form akin to ichneuo, "to trace out" (ichnos, "a footprint, a track"), is translated "unsearchable" in Ephesians 3:8, of the riches of Christ; in Romans 11:33, "past tracing out," of the ways of the Lord (cp. No. 1, in the same verse). The ways of God are the outworkings of His judgment. Of the two questions in Romans 11:34, the first seems to have reference to No. 1, the second to No. 2. See FIND, Note