leer (v.) Look up leer at Dictionary.com
"to look obliquely" (now usually implying a lustful or malicious intent), 1520s, probably from Middle English noun ler "cheek," from Old English hleor "the cheek, the face," from Proto-Germanic *khleuzas "near the ear," from *kleuso- "ear," from PIE root *kleu- "to hear" (see listen). If so, the notion is probably of "looking askance" (compare the figurative development of cheek). Related: Leered; leering.
leer (n.) Look up leer at Dictionary.com
1590s, from leer (v).