The word איברא only appears a handful of times in the Talmud. (E.g. Pesachim 104a; Chulin 59b, 60a) it means something like its true, you’re right etc. What is the true meaning of this word, it’s literal meaning, how is it formed? I would think it’s a verb form of ברא but that wouldn’t make much sense. In Shabbos 90b, it is used meaning arm [אבר] but that still doesn’t fit with the above examples.
Marcus Jastrow says the word means "indeed" or "to be sure".
Everytime you have a question concerning Talmudic vocabulary, it would be a good idea to check Jastrow first. A physical copy is a great thing to have on the bookshelf, but you can access the dictionary online here.