Althea, from Greek Ἀλθεία, was Meleager's mother's name and is also the Latin scientific name of the marshmallow plant, Althaea officinalis. In ancient Greek, ἀλθεία could also designate the mallow (Malva).
The name comes from the root ἀλθαι-, "heal", which gave the verb ἀλθαίνω. Ἀλθαία merely means "healing substance", which refers to the way this medical plant was used during Antiquity.
Source: Dictionnaire étymologique de la langue grecque by Pierre Chantraine.
The Grateful Dead have a well-known song called Althea. Many Dead fans believe the song makes reference to both the mother of Meleager and Leda (Helen of Troy's mother) in Greek Mythology and a poem by Richard Lovelace, "To Althea, From Prison" in the 1600s.