WHERE DO WE GET THE PHRASE "SLEEP TIGHT" FROM?
It comes from Shakespearean England via thousands of children's bedtimes. William Shakespeare first gave "tightly" the meaning "effectively" or "well" in his 1598 play THE MERRY WIVES OF WINDSOR, where Falstaff asks a servant to deliver "these letters tightly". by the late 18th century, the word was also used as an adjective, and it was in this form that it become part of the rhyming couplet "Good night. Sleep tight," probably dreamed up by an anonymous mother to wish her young children a pleasant sleep. the subsequent popularity of this rhyme means that the phrase lives on today, despite its exact meaning being largely forgotten.