tear, nasal discharge
洟 centers on bodily fluids from the face: tears from the eyes and nasal discharge from the nose. Both are liquid secretions that flow from the head.
洟 combines 氵 (water) with 夷, which likely contributes the sound. The character represents watery secretions from the face.
The water radical 氵 beside 夷 suggests liquid flowing from the face. Picture tears and nasal discharge as water that the body releases.
For イ, imagine an itchy nose and eyes causing tears and discharge: itchy -> イ, and the water flows.