> > Mac Onlea could easily come from the reduction of Mac Dhonnshléibhe.
> I think I understand why the "Dh" and the "sh" in Mac Dhonnsliebhe is
> lenited, but I'm a bit confused about the rules for muting of the "bh".
Let me outline the changes, as I "hear" them, to find out if others
1. The broad "dh", written in IPA as a gamma, is homorganic with
the "c" in "mac", and they simply coalesce;
2. The "sh" is pronounced as /h/, but often weakly in non-initial
position, especially between consonsants;
3. The slender "bh" is a bilabial /v’/, but the ending that would
be carefully pronounced /e:v’@/ could easily be curtailed to /e:/.
Mac Dhonnshléibhe > Mac (Dh)onn(sh)léi(bhe)
Also, I think that the Livingston(e)/Donlevy family were hereditary
physicians in Ulster, so the reinterpretation of their name as
Mac an Léigh (= Son of the Physician; see OI "líaig") would both
make sense and would fit exactly with the anglicization MacOnlea.