WP-QDA Marked Text is a plugin for WordPress designed for rudimentary Qualitative Data Analysis (QDA).
Please see the direction on the website: http://www.ryantcragun.com/wp-qda-marked-text/
Depending on the nature of the text you are coding, you may also consider downloading the plugin "Private! WordPress Access Control Manager". While that plugin is a little complex for the purpose here, it does make it so posts are private by default, meaning only those individuals with an account on your installation can view the posts and retrieve text.