Puhoy is a meme, originated on tumblr because of a title Adventure Time episode that hadn’t aired yet.
“Puhoy” was largely started by tumblr user “sushiprincess”. Eventually a Puhoy confession blog was started by that user. A lot of the popularity was because of the silly sounded nature of the word. Often people would post statements replacing words with Puhoy, such as song lyrics or sayings, such as “You know the old saying, children should be puhoyed and not heard”