If I understand your question correctly, and you want to generate the following XML from your sample XML:
<?xml version="1.0" encoding="UTF-16"?>
<items>
<items-items>3</items-items>
</items>
then the following XSLT can be used:
<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output indent="yes" />
<xsl:template match="@*|node()">
    <xsl:copy>
        <xsl:apply-templates select="@*|node()"/>
    </xsl:copy>
</xsl:template>
<!--Match elements who's name is equal to it's parent -->
<xsl:template match="*[name()=name(..)]">
    <!--create an element using the name of the parent element, followed by a "-", followed by the matched element name -->
    <xsl:element name="{name(..)}-{name()}">
        <xsl:apply-templates select="@*|node()"/>
    </xsl:element>
</xsl:template>
</xsl:stylesheet>