User blog comment:Varzan Deodinm Beldinm/Yang enters DEATH BATTLE (teaser)/@comment-26512661-20151007143420/@comment-11188061-20151007150536

Well, it's an educated guess. Ruby was taught by Qrow and Taiyang hasn't made an appearance in a million years, so it's plausible that Qrow was the one who taught her how to street punch. He is a cool uncle after all.