I have a client in the US (Illinois) who calls their custom admin panels the &quot;back room&quot; or sometimes &quot;back end&quot;. For example, they will say something like &quot;We&#x27;ll just create the account in the back room&quot;. We always work in English. I cannot say I have encountered &quot;back office&quot;, but it doesn&#x27;t sound too awkward. I wouldn&#x27;t be surprised by an admin panel being called the &quot;back office&quot;, although personally I usually use the term &quot;admin panel&quot; since it&#x27;s quick and less ambiguous.