Mac Seancha
Mac SEANCHA, Mac SEANCHAIDHE—VII—MacShanaghy, Shanaghy, Shanahy, and, by 'translation,' Fox; 'son of the historian,' or 'antiquary' (Irish seancha, seanchaidhe); the name of a family originally from Co. Sligo, but now found chiefly in Co. Leitrim. Fox is an incorrect translation, being founded on the erroneous supposition that the surname is derived from 'sionnach,' a fox.
Alphabetical Index to Irish Surnames