From Longman Dictionary of Contemporary Englishtwaintwain /tweɪn/ number old use 1 TWOtwo2 → never the twain shall meet
Examples from the Corpus
twain• She held up her axe to ward off a murderously diving spar, and split it in twain.• Generally, the streetwise dealers work in a separate camp from the more educated types, and never the twain shall meet.Origin twain Old English twegen 