IBBY:  see Isabel.

IDA:  Probably Old English name meaning "prosperous."

ILEEN:  see Eileen.

ILSE:  see Elizabeth.

IMMY:  see Imogen.

IMOGEN:  Latin name meaning either "last-born" or "daughter."  Variant, Imogene, exists.  Diminutive is Immy.

IMOGENE:  see Imogen.

INA:  Latin suffix used to feminize female names.  Variant, Ena, exists.

INDIA:  From the country name. 

INDIANA:  Either from the U.S. state.  Diminutive is Indy.

INDY:  see Indiana.

INGA:  see Ingrid.

INGE:  see Ingrid.

INGRID:  Scandinavian name meaning "fair; beautiful."  Variants include Inga and Inge.

IOLANTHE:  Greek name meaning "violet flower."

IONA:  From Greek place name meaning "from the king's island."  Variant, Ione, exists.

IRENE:  Greek name meaning "peace."  Variant is Rene, exists.

IRIS:  Greek name meaning "rainbow."

IRMA:  Old German name meaning "whole; universal."

ISA:  see Isabel.

ISABEL:  Spanish from of Elizabeth, "pledged to God."  Variants include Isabella and Isobel.  Some diminutives are Bella, Ella, Ibby, Isa, Nib, and Sib.

ISABELLA:  Italian form of Elizabeth, "pledged to God."  French variant, Isabelle, exists.

ISABELLE:  see Isabella.

ISADORA:  Feminine form of Isidore, "gift of Isis."  Variant, Isidora, exists.  Diminutives include Issy and Izzy.

ISIDORA:  see Isadora.

ISLA:  From name of Scottish river.

ISOBEL:  Variant form of Isabel, "pledged to God."

ISOLDA:  see Isolde.

ISOLDE:  Possibly a Welsh name meaning "fair lady." Variant, Isolda, exists.

ISSY:  see Isadora.

IVY:  From the plant.

IZZY:  see Isadora.