The word "thrithing" is spelled with a silent "r" and pronounced as "thray-thing". The correct spelling is actually "thriving", which means to prosper or flourish. The common misspelling may have originated from a mispronunciation of the word or confusion with the similarly spelled word "thrashing". However, it is important to use the correct spelling to maintain clarity and credibility in written communication. The correct pronunciation and spelling of words can enhance language proficiency and communication skills.