Why Is It Called "Mischief Night"?
For most of the country, the day before Halloween is known simply as October 30th. But for people in the Philadelphia and New Jersey area, the evening before All Hallow's Eve is known as "Mischief Night," a celebration of pranks and light marauding.
The name comes from the UK, where the night is still celebrated in some counties (although often on different dates and under different names). The Guardian reports that the earliest known appearance of the term is from 1790, in writings about a Headmaster at St John's College, Oxford who had "encouraged a school play which ended in 'an Ode to Fun which praises children's tricks on Mischief Night in most approving terms.'"
Nowadays, most kids skip the theatrical performance and go straight for the toilet-papering.
Other names for the evening include "Devil's Night" (Michigan), "Cabbage Night" (Vermont and New Hampshire)," and "Devil's Eve" (Arkansas). Check out Slate for a full map tracking the geographic epicenters of all this mischievousness.