Abarim Publications' online Biblical Greek Dictionary
θαρσος
The noun θαρσος (tharsos) means courage, the grounds of confidence (Acts 28:15 only). It stems from the same Proto-Indo-European root "dhers-", meaning to dare or be bold as our English verb to dare. Note the pleasing but accidental similarity with the name ταρσος (tarsos), Tarsus, of the city from which Paul hailed. Several old school scholars, including Josephus, believed that Tarsus was the same as Tarshish, which in Greek is indeed spelled Θαρσος (Tharsos), identical to our noun. From our noun derive:
- The verb θαρρεω (tharreo), meaning to be confident, to have courage, to be of good cheer. The difference between this verb and the next one is a mere matter of dialect. This verb is Attic (used in Athens and environs), whereas the next verb is Doric-Ionic-Aeolic (everywhere else). This Attic verb occurs 6 times; see full concordance.
- The verb θαρσεω (tharseo) also means to be confident, to have courage, to be of good cheer. As said above, it's the same verb as the former, but from a different Greek dialect. In the New Testament, this verb is used solely in the imperative mood: have courage! be confident! It's used 8 times; see full concordance.