Likho is not a real proper name, but a noun meaning bad luck in modern Russian (Don't wake likho while it's quiet proverb), similar to Polish (sayings "Cicho! Licho nie śpi" -Quiet! Licho does not sleep, "Licho wie" -Licho knows = only licho knows – nobody knows). In old Russian the root meant "excessive", "too much" with pejorative connotations. Compare to Russian lishniy - one in excess. The word is likely to be related to Indo-European leikw meaning something to remain, to leave. The derived adjective likhoy can be used to describe someone who is a bit too daring or brave. In Czech, lichý means odd (number), idle, vain. In Polish, lichy means shoddy, poor, flimsy. In Belarusian language, ліхі means bad, evil (like in prayer), odd (side of clothing).
There are several basic versions of tales how a person meets with Likho, with different morals of the tale.
Within the framework of superstitions, Likho was supposed to come and eat a person. In particular, this was used to scare small children.
Recently, some Slavic neopagans attempt to "retrofit" Likho into the Slavic Pantheon.