與 and 牙 don't sound similar in modern Mandarin due to historical phonetic changes. They were more similar in older Chinese.與 /*m-q(r)aʔ/, /*ɢ(r)aʔ-s/ 牙 /*m-ɢˤ<r>a/
Due to historical stylistic changes, this component is less similar to 牙 than it was in ancient scripts.