The spelling of the word "eating tetter" may seem unusual to some. However, the IPA phonetic transcription can shed light on why it is spelled this way. The word "eating" is pronounced as /ˈiːtɪŋ/, with the "ea" being pronounced as a long "e" sound. Meanwhile, "tetter" is pronounced as /ˈtɛtər/, with the emphasis on the first syllable. Despite its quirky spelling, "eating tetter" refers to a commonly seen condition characterized by rash-like lesions that occur around the mouth.
Lupus.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.