The name of the Lord is a strong tower;
the righteous man runs into it and is safe.
Proverbs 18:10, ESV
In this passage, strong is the hebrew word `oz (oze) meaning force, security, majesty, praise, boldness, strength, power, loud, strong. It comes from the root word `azaz (aw-zaz') which means to be stout, harden, impudent, prevail, strengthen, be strong.
The word tower is the hebrew word migdal (mig-dawl') meaning tower, rostrum, castle.
*Strong, James, LL.D., S.T.D., The New Strong's Expanded Exhaustive Concordance of the Bible, Red Letter Edition (Expanded With the Best of Vine's Dictionary of Old & New Testament Words) (Nashville: Thomas Nelson, 2010). (H5797, H5810, H4026)