It&#x27;s not just historical.  &quot;Ů&quot; is phonologically a longer &quot;u&quot;, but it is actually an alternation [1] of &quot;o&quot;: for example see how nominative &quot;dům&quot; becomes &quot;domu&quot; in the genitive (likewise &quot;stůl&quot;, &quot;bůh&quot;, etc.).  When a &quot;u&quot; becomes longer, instead, it becomes a &quot;ú&quot; as the first letter of the word, but otherwise it becomes &quot;ou&quot;; for example see how the feminine nominative of (some) nouns and adjectives is &quot;a&quot; and &quot;á&quot; respectively, while the accusative is &quot;u&quot; and &quot;ou&quot;, or how the perfective companion of &quot;kupovat&quot; is &quot;koupit&quot;.<p>(Also, see how I sneaked in a &quot;Ů&quot; in the second sentence :)).<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Alternation_%28linguistics%29" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Alternation_%28linguistics%29</a>