I think the &quot;making sense&quot; refers to the fact that &quot;billion&quot; has &quot;bi-&quot; as a prefix, and &quot;trillion&quot; has &quot;tri-&quot; as a prefix.  In American English, it&#x27;s not clear what is &quot;bi-&quot;, exactly, about a billion -- two of what?<p>If we had skipped &quot;billion&quot; and gone with &quot;trillion&quot; = 1e9, then it would be more natural, because then it would refer to the number of thousands; but then the more natural nomenclature would be &quot;bi-sands&quot; and &quot;tri-sands&quot; or something.