moonlight
v.
"hold a second job, especially at night," 1957 (implied in moonlighting), from moonlighter (1954), from the notion of working by the light of the moon; see moonlight, n.. Related: Moonlighting. Earlier the word had been used to mean "commit crimes at night" (1882).
n.
"light of the moon," mid-14c., from moon, n. + light, n..