Sources

“Powmachorne, Polmathorne, -mothorne 1512 Treas. Acc.; Pomathorn 1676-1755 SHS I. 13. Pamathorn 1773 Arm.

On the analogy of Polmadie (near Glasgow) (Polmacde 1179-89) ‘pool or hollow of the sons of Daigh’ or some such pers. name, CPNS 203-4, this appears to be “hollow of the sons of ? Thor(n).” The first el. v. Gael. poll, is an exact topographical description of the modern Pomathorn. For the second el. Watson notes (CPNS 204) the frequent dropping of c. from mac. The third el. is obviously a pers. name, probably Thore as in ‘Thorfynn mac Thore’ quoted by Watson CPNS 133, probably to be equated with Gaelic torun ‘thunder’.” Dixon, 342