It really depends what you mean by &#x27;traditionally&#x27;. My reading of [1] is that the &#x27;ka&#x27; reading is one of many although it&#x27;s become more prevelant in modern usage. [2] says that &#x27;papa&#x27; was most common in Old Japanese.<p>[1] <a href="https:&#x2F;&#x2F;en.wiktionary.org&#x2F;wiki&#x2F;%E6%AF%8D#Japanese" rel="nofollow">https:&#x2F;&#x2F;en.wiktionary.org&#x2F;wiki&#x2F;%E6%AF%8D#Japanese</a><p>[2] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Mama_and_papa" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Mama_and_papa</a>