Miley

In the case of actress and singer Miley Cyrus (1992-), it is a shortened form of the nickname Smiley, given to her by her father because she often smiled. Although it was not at all common before she brought it to public attention, there are some examples of its use before her time, most likely as a diminutive of MILES.

MILES   male   English
From the Germanic name Milo, introduced by the Normans to England in the form Miles. The meaning is not known for certain. It is possibly connected to the Slavic name element milu meaning "gracious". From an early date it was associated with Latin miles "soldier".
OTHER FORMS
ANCIENT GERMANIC: Milo
BULGARIAN: Mila, Milan, Milen, Milena, Milka, Milko
CROATIAN: Mijo, Mila, Milan, Milana, Milanka, Mile, Milena, Milenko, Milica, Miljenko, Milka, Miloš
CZECH: Mila, Milada, Milan, Milana, Milena, Miloš
DUTCH: Milan
ENGLISH: Miles, Milo, Myles
FRENCH: Mylène
HUNGARIAN: Milán, Miléna
ITALIAN: Milena
MACEDONIAN: Mila, Milan, Mile, Milena, Milica, Milka, Miloš
MEDIEVAL SLAVIC: Mila, Milada, Milan, Mile, Militsa, Milka, Milko, Miloje, Milosh
POLISH: Milena, Miłosz
RUSSIAN: Mila, Milan, Milena
SERBIAN: Mijo, Mila, Milan, Milana, Milanka, Mile, Milena, Milenko, Milica, Miljana, Milka, Miloje, Milojica, Miloš
SLOVAK: Milan, Miloš
SLOVENE: Milan, Milena, Milica, Milka, Miloš
UKRAINIAN: Mila