The name Lettie is a girl's name of English origin meaning "joy, gladness". Lettie and is often added to lists like Nicknames for Girls and discussed in our forums with posts like "The Makeover Baby Name Game".
From the experts:
Lettie, also spelled Letty, is a nickname name not heard in over a century, giving it the patina of a treasured antique. Lettie's style currency is rising with the trend for old-fashioned, down-to-earth nicknames. Lettie is right in step with Lottie, Hettie, Hattie, Josie, and Maisie.
One of Joan Crawford's early hit roles was in 1932 as the eponymous heroine of the film Letty Lynton, in which she wore a dress--dubbed the Letty Lynton dress--that became a national fad.