涂
tú · HSK 7
to apply
🖌️ tú = 氵water radical + 余; a watery liquid you spread and smear on
The water radical 氵 marks 涂 as something wet and spreadable, like paint or lacquer daubed onto a surface. Sound hook: tú rhymes with goo, the stuff you smear, daub, and blot out.
涂 — water radical 氵 + 余 (phonetic)
涂 is a phono-semantic compound: the 氵 water radical hints at the meaning, while 余 supplies the sound 'tu/yu'. Originally it referred to a river name and to mud or wet earth, which extended to the verb sense 'to smear, daub, or apply' something wet like paint or mud onto a surface.