spell correct and add single quotes

docs/reference/analysis/analyzers/custom-analyzer.asciidoc

@@ -5,7 +5,7 @@ An analyzer of type `custom` that allows to combine a `Tokenizer` with
 zero or more `Token Filters`, and zero or more `Char Filters`. The
 custom analyzer accepts a logical/registered name of the tokenizer to
 use, and a list of logical/registered names of token filters.
-The name of the custom analyzer must not start mit "_".
+The name of the custom analyzer must not start with "_".
 
 The following are settings that can be set for a `custom` analyzer type:
 

src/main/java/org/elasticsearch/index/analysis/AnalysisService.java

@@ -253,7 +253,7 @@ public class AnalysisService extends AbstractIndexComponent implements Closeable
 
         for (Map.Entry<String, NamedAnalyzer> analyzer : analyzers.entrySet()) {
             if (analyzer.getKey().startsWith("_")) {
-                throw new IllegalArgumentException("analyzer name must not start with _. got \"" + analyzer.getKey() + "\"");
+                throw new IllegalArgumentException("analyzer name must not start with '_'. got \"" + analyzer.getKey() + "\"");
             }
         }
         this.analyzers = ImmutableMap.copyOf(analyzers);