Any text that starts with a capital letter, and contains another capital letter within it is called "CamelCase", and is treated as an automatic "WikiLink" reference to a tiddler (even if that tiddler doesn't exist yet).
You can disable this handling in several ways:
1) For single occurrences, just precede the text with "~", as in "~MacInnes"
3) Disable automatic WikiLinks in the whole file, by clearing the "Enable automatic CamelCase linking" checkbox in $:/ControlPanel, Settings tab or by directly setting the text content of $:/config/WikiParserRules/Inline/wikilink to "disable".
enjoy,
-e