The phrase "gat bottom of" may seem puzzling as it is not commonly used in modern English. However, it is thought to originate from the Scottish dialect, where "gat" means "got" and "bottom of" means "at the bottom of". The pronunciation of "gat" is transcribed as /ɡæt/ in IPA phonetic transcription, with the "a" pronounced as in the word "cat". Therefore, the correct spelling of this phrase would be "got bottom of".