Asseses the various attempts at an etymology of this word (cf. T. F. O’Rahilly, in Ériu 9 (1923), pp. 18-19, T. S. Ó Máille, in Éigse 11/1 (1964), pp. 20-21, R. A. Breatnach, in Éigse 11/3 (1966), p. 159) and adheres to E. Knott’s suggestion of a derivation from Engl. pleurisy; also on the borrowing of p- as p- and f-).