Apart from Medicine the Callanans were prominent Apothecaries in Cork:

https://docs.google.com/spreadsheets/d/17Xdk_bdkpBSVHaTP45WxSY0r4v6-kluvlPz7ZynQxfU/edit#gid=0

Callnan family hereditary Physicians to the McCarthy Riabhachs, 1798 in West Cork, Dr. John Richard Elmore owner of largest Linen Mill in Munster in Clonakilty 1820s and Dr. William and Albert Callnan, Clonakilty.

The head of the Dunmanway McCarthys, Gerry na Duna, eloped c 1750 with a iss Calnan of Clonakilty they later separated.

From the Southern Star:
1798 Leader in Clonakilty: Interesting story of Dr William Callanan
The Southern Star, Saturday February 4th, 1978
Many people regret that they allowed some old seanachaí to take his lore to the grave with him. Indeed, oral tradition often adds colour and warmth to our past. But it often falls down on accuracy and perspective. In recent years an old man, since dead, was certain that his grandfather had watched Cromwell burning Timoleague friary.
Fortunately, we know that even the grandfather’s…