Sources

Sraithibh (‘Sraithu’); The Gaelic name. . . however, is Sraithibh a locative plural of srath and meaning ‘at or in the Straths’: Robertson 2019, p. 308

“… ‘Sryoo’ for Strathfillan. Clearly I suggest “Sradhaibh” plur. dative or locative of strath. The Perthshire dialect invariable turns these “aibh” into (oo) u.”  West Perthshire Place-names, Oban Times March 5^th 1910

Sryu Diack MS2276