The spelling of the word "thweatt" is quite unique and can be easily explained through the use of IPA phonetic transcription. The first sound is the voiceless dental fricative "θ," followed by the voiced bilabial stop "b." The next letter is the voiced labiodental fricative "v," and the final sound is the voiceless alveolar plosive "t." Thus, "thweatt" is spelled as it is pronounced: θwæt. Wouldn't it be easier to spell it phonetically as "thwat"?