The spelling of "gill rod" can be explained using the International Phonetic Alphabet (IPA). "Gill" is pronounced with a hard g (ɡ), followed by a short "ih" sound (ɪ) and a double "L" (lː). "Rod" is pronounced with a short "o" sound (ɑ) followed by a "d" (d). Together, the two words form a compound noun that is often used in the fishing industry to refer to a tool used for measuring the size of fish gills. The spelling of this word may seem unusual but it accurately reflects the pronunciation.