This is similar to most dynamic/scripting languages of that era, for that matter; both Perl and Ruby (and, IIRC, PHP) have similar conventions. Things got bungled when Java programmers started insisting on camelCased function names even outside of Java.
Things got bungled when Smalltalk used an old version of ASCII which had a backarrow instead of underscore. Smalltalk used backarrow for assignment and had no way to separate words in identifiers other than CamelCase. Smalltalk programmers kept this convention when they moved to Java, even though the technical limitation was gone and they could have used a more legible style.
