L/R split
The mutual interchange in words of the sounds of l and r is by no means an exclusively Irish characteristic, but a linguistic phenomenon of world-wide occurrence. Nevertheless it is an extremely frequent form of alteration in Irish words, as may be endlessly demonstrated. For example the borrowed word "orange" enters Irish as óráiste and is then corrupted to laiste; such doublets are commonplace as biorar/biolar, mairc/mailc, aibghidir/aibidil, and goile/goire; such a word as sruthair, "stream" is frequently pronounced in such fashion as to give rise to anglicisation in place-names as Shrule, Shruel, Struell, and Sroohill. But these instances are not particularly illuminative of Finnegans Wake.
All things considered, however, it has been thought best to gloss all important occurrences of L/R Interchange in Finnegans Wake, not even primarily because of the frequency of the phenomenon in Irish, but because of the frequency with which Joyce makes use of it in Irish contexts, and especially in conjunction with the much more distinctive *P/K Split. Reference to the *P/K Split, for instance, permits the restoration of "roman pathoricks" (027.02) to "roman cathoricks"; but only further invocation of the L/R Interchange permits us the full reconstruction "roman catholicks."
