Abarim Publications' online Biblical Hebrew Dictionary
There are two roots of the form בטח (batah), although the second one may not have ever existed:
The root-verb בטח (batah I) means to trust, feel safe or be confident (Psalm 33:21, Isaiah 12:2). With the particle ב (be) prefixed, it means to trust in (2 Kings 18:5, Psalm 41:9, Isaiah 26:3). In conjunction with the particle על ('l) it means to rely upon (Psalm 31:14, Jeremiah 49:11), and with אל ('l) it means trust to (2 Kings 18:22, Psalm 4:5).
Our verb בטח (batah) "expresses that sense of well-being and security which results from having something or someone in whom to place confidence" (in the words of HAW Theological Wordbook of the Old Testament).
The objects of this verb are varying widely, from things (Deuteronomy 28:32) to persons (Judges 9:26), but mostly God (Psalm 9:11).
The derivatives of this verb are:
- The masculine noun בטח (betah), meaning safety or security (Genesis 34:25, Isaiah 32:17). This word is mostly used as an adverb meaning securely (Leviticus 25:18, Judges 18:7, Isaiah 14:30).
- The feminine noun בטחה (beteha), meaning trust of trusting (Isaiah 30:15 only).
- The masculine noun בטחון (bittahon), meaning confidence or trust (2 Kings 18:19, Ecclesiastes 9:4).
- The feminine plural noun בטחות (battuhot), meaning security or safety (Job 12:6 only).
- The masculine noun מבטח (mibtah), meaning (1) the act of confiding (Proverbs 21:22); (2) The object of confidence (Job 8:14, Jeremiah 2:37); (3) The state of confidence (Proverbs 14:26, Isaiah 32:18).
Root בטח (bth II) may not be a true Hebrew root, since its sole (assumed) derivative is the masculine plural noun אבטחים ('abattihim), meaning watermelons. This noun occurs only once, in Numbers 11:5 and may very well have been imported into the Hebrew language along with the fruit.