Sorry not to have replied earlier but I had changed my email address.
As far as I can ascertain the 'Iland' part is an agnomen and was used to differentiate between close family members. So you would have O'Donovan-Baad, O'Donovan-Rossa etc. O'Donovan-Iland was I am sure originally Island and was most likely to identify the O'Donovan family living on Inchydoney Island close to Clonakilty, Co Cork.
Not sure that helps you much I am afraid