Adelaide \a-delai-de, ad(e)-laide\ as a girl's name is pronounced AD-a-layd. It is of Old German origin, and the meaning of Adelaide is "noble kind". First popular in England after the reign (1830-37) of William IV and Queen Adelaide. She was a German princess who accepted the young prince after he'd been turned down by seven other noble ladies. The city of Adelaide, Australia, founded in 1836, was named for her. Adelheid is the Dutch and German form; Adalheid is German; Adelaida is Polish.
Adelaide has 57 variant forms: Ada, Adalaide, Adalayde, Adalena, Adalheid, Adalin, Adaline, Adalyn, Addala, Addalla, Adde, Addey, Addi, Addie, Addy, Adel, Adela, Adelade, Adelaida, Adelais, Adelajda, Adele, Adelei, Adelheid, Adelia, Adelina, Adeline, Adelice, Adelicia, Adelis, Adell, Adella, Adelle, Adelyn, Adelynn, Adey, Adi, Ado, Ady, Aide, Alice, Aline, Aliosha, Alline, Alyosha, Del, Dell, Della, Delle, Delli, Delly, Edeline, Eline, Elke, Heidi, Lady and Laidey.
For more information, see also the related name Adalia.