The word "疥疮" is formed by combining the character "疥", which itself consists of the sickness radical "疒" and the phonetic component "介" to indicate scabies, with the character "疮", composed of the same sickness radical "疒" and the phonetic "仓" to denote a sore or ulcer, resulting in a compound where both characters semantically contribute to define the specific skin condition scabies.