Tiras is a son of Japheth, son of Noah (Genesis 10:2).
The name Tiras is difficult to interpret because there is nothing in the ancient Hebrew language that looks like it. NOBS Study Bible Name List doesn't even try to translate and leaves a meaning blank. Jones' Dictionary of Old Testament Proper Names mentions no possible Hebrew roots and goes straight to an Arabic verb, and renders the meaning Desire.
The word (tiras) is the modern Hebrew word for maize, but Klein's Etymological dictionary of the Hebrew Language firmly protests against it ("far and forced is the way in which this proper name came to denote maize or corn").
Fuerst's Hebrew & Chaldee lexicon to the Old Testament points out the unused root thrs and that (back to Klein's Etymological dictionary of the Hebrew Language) means to separate priestly dues; to contribute, donate; having to do with separation, consecration.
Perhaps the name is a construct of the letter taw plus a derivation of the root (rasas), to moisten, or (rss), the assumed root of (rasis), fragment. The latter may have helped to form the modern word for maize.
(rasas), to moisten, or 
