耆 and 旨 don't sound similar in modern Mandarin due to historical phonetic changes. They were more similar
in older Chinese.
Character Evolution
BronzeLate Spring and Autumn~500 BCSealWarring States (Chu)475-221 BCSealShuowen~100 ADClericalQin221-206 BCClericalWestern Han202 BC-9 ADClericalEastern Han25-220 ADRegularModern