Documentation 
Section: the first one I found was a log message:

./libxslt/transform.c:                     "freeing transformation dictionnary\n");

dictionnary

Correct version:
dictionary

Other information:
here's a grep of all the occurrences:

[pawlowski@dev libxslt-1.1.15]$ find . -name '*.*'  -exec grep -Hn dictionnary \{\} \;
./libxslt/documents.h:62: * @dict: the dictionnary to use when parsing that document
./libxslt/xsltInternals.h:431:     * dictionnary: shared between stylesheet, context and documents.
./libxslt/xsltInternals.h:562:     * dictionnary: shared between stylesheet, context and documents.
./libxslt/xslt.c:2450:               * the dictionnary should be shared since nodes are
./libxslt/xsltutils.c:79: *         in the stylesheet dictionnary.
./libxslt/xsltutils.c:597: * @dict: a dictionnary
./libxslt/xsltutils.c:601: * Split QNames into prefix and local names, both allocated from a dictionnary.
./libxslt/documents.c:47: * @dict: the dictionnary to use when parsing that document
./libxslt/transform.c:351:     * setup of the dictionnary must be done early as some of the
./libxslt/transform.c:526:                     "freeing transformation dictionnary\n");
./libxslt/transform.c:669: * @interned:  the string is in the target doc dictionnary
Binary file ./libxslt/.libs/libxslt.a matches
Binary file ./libxslt/transform.o matches
./python/libxslt-python-api.xml:19:      <arg name='params' type='pythonObject' info='the parameters dictionnary'/>
./doc/libxslt-api.xml:846:      <field name='includes' type='xsltDocumentPtr' info='* dictionnary: shared between stylesheet, context and documents.
./doc/libxslt-api.xml:934:      <field name='parserOptions' type='int' info='* dictionnary: shared between stylesheet, context and documents.
./doc/libxslt-api.xml:1273:      <arg name='dict' type='xmlDictPtr' info='the dictionnary to use when parsing that document'/>
./doc/libxslt-api.xml:1600:      <return type='const xmlChar *' info='the attribute value or NULL if not found. The string is allocated in the stylesheet dictionnary.'/>
./doc/libxslt-api.xml:2277:      <info>Split QNames into prefix and local names, both allocated from a dictionnary.</info>
./doc/libxslt-api.xml:2279:      <arg name='dict' type='xmlDictPtr' info='a dictionnary'/>
./doc/libxslt-refs.xml:3500:        <word name='dictionnary'>
./doc/libxslt-refs.xml:3505:        <word name='dictionnary:'>
./doc/xslt.html:307:      libxml2 memory management for text nodes, dictionnary text bug, forbid
./doc/xslt.html:336:  <li>extensions: module support (Joel Reed), dictionnary based speedups
./doc/xslt.html:416:  <li>performance: use dictionnary lookup for variables</li>
./doc/xslt.html:423:    &lt;xsl:message&gt; halt, OpenVMS fix, dictionnary reference counting
./doc/xslt.html:438:    interfaces, dictionnary reuses for XSLT with potential for serious
./doc/xslt.html:1361:transformation is passed a dictionnary of parameters. Note that the string
./doc/APIchunk3.html:108:</dd><dt>dictionnary</dt><dd><a href="html/libxslt-documents.html#xsltDocLoaderFunc">xsltDocLoaderFunc</a><br />
./doc/APIchunk3.html:111:</dd><dt>dictionnary:</dt><dd><a href="html/libxslt-xsltInternals.html#_xsltStylesheet">_xsltStylesheet</a><br />
./doc/news.html:17:      libxml2 memory management for text nodes, dictionnary text bug, forbid
./doc/news.html:40:  </li><li>extensions: module support (Joel Reed), dictionnary based speedups
./doc/news.html:89:</ul><h3>1.1.5: Mar 23 2004</h3><ul><li>performance: use dictionnary lookup for variables</li>
./doc/news.html:96:    &lt;xsl:message&gt; halt, OpenVMS fix, dictionnary reference counting
./doc/news.html:103:    interfaces, dictionnary reuses for XSLT with potential for serious
./doc/python.html:148:transformation is passed a dictionnary of parameters. Note that the string
./doc/html/libxslt-documents.html:30:</pre><p>An <a href="libxslt-documents.html#xsltDocLoaderFunc">xsltDocLoaderFunc</a> is a signature for a function which can be registered to load document not provided by the compilation or transformation API themselve, for example when an xsl:import, xsl:include is found at compilation time or when a document() call is made at runtime.</p><div class="variablelist"><table border="0"><col align="left" /><tbody><tr><td><span class="term"><i><tt>URI</tt></i>:</span></td><td>the URI of the document to load</td></tr><tr><td><span class="term"><i><tt>dict</tt></i>:</span></td><td>the dictionnary to use when parsing that document</td></tr><tr><td><span class="term"><i><tt>options</tt></i>:</span></td><td>parsing options, a set of xmlParserOption</td></tr><tr><td><span class="term"><i><tt>ctxt</tt></i>:</span></td><td>the context, either a stylesheet or a transformation context</td></tr><tr><td><span class="term"><i><tt>type</tt></i>:</span></td><td>the <a href="libxslt-documents.html#xsltLoadType">xsltLoadType</a> indicating the kind of loading required</td></tr><tr><td><span class="term"><i><tt>Returns</tt></i>:</span></td><td>the pointer to the document (which will be modified and freed by the engine later), or NULL in case of error.</td></tr></tbody></table></div><br />
./doc/html/libxslt-xsltInternals.html:220:    <a href="libxslt-xsltInternals.html#xsltDocumentPtr">xsltDocumentPtr</a>  includes        : * dictionnary: shared between stylesheet
./doc/html/libxslt-xsltInternals.html:293:    int       parserOptions   : * dictionnary: shared between stylesheet
./doc/html/libxslt-xsltutils.html:124:<div class="variablelist"><table border="0"><col align="left" /><tbody><tr><td><span class="term"><i><tt>style</tt></i>:</span></td><td>the stylesheet</td></tr><tr><td><span class="term"><i><tt>node</tt></i>:</span></td><td>the node</td></tr><tr><td><span class="term"><i><tt>name</tt></i>:</span></td><td>the attribute name</td></tr><tr><td><span class="term"><i><tt>nameSpace</tt></i>:</span></td><td>the URI of the namespace</td></tr><tr><td><span class="term"><i><tt>Returns</tt></i>:</span></td><td>the attribute value or NULL if not found. The string is allocated in the stylesheet dictionnary.</td></tr></tbody></table></div><h3><a name="xsltGetDebuggerStatus" id="xsltGetDebuggerStatus"></a>Function: xsltGetDebuggerStatus</h3><pre class="programlisting">int    xsltGetDebuggerStatus(void)<br />
./doc/html/libxslt-xsltutils.html:172:</pre><p>Split QNames into prefix and local names, both allocated from a dictionnary.</p>
./doc/html/libxslt-xsltutils.html:173:<div class="variablelist"><table border="0"><col align="left" /><tbody><tr><td><span class="term"><i><tt>dict</tt></i>:</span></td><td>a dictionnary</td></tr><tr><td><span class="term"><i><tt>name</tt></i>:</span></td><td>the full QName</td></tr><tr><td><span class="term"><i><tt>prefix</tt></i>:</span></td><td>the return value</td></tr><tr><td><span class="term"><i><tt>Returns</tt></i>:</span></td><td>the localname or NULL in case of error.</td></tr></tbody></table></div><h3><a name="xsltTimestamp" id="xsltTimestamp"></a>Function: xsltTimestamp</h3><pre class="programlisting">long xsltTimestamp                   (void)<br />