PIE verbal root *IEG[H] ???

I was wondering if anybody on the list was aware of a PIE root which would
give a Celtic verb Ieg- (found in a recent Gaulish inscription).
The most likely candidate would seem to be something like (in Pokorny's
terms) *IEG- / *IEGH- (I am aware of the root meaning "Ice," but I am
looking for a verbal root instead).
The Gaulish verb in question seems to be related to PIE *IEK- "speek," but
this should give a Gaulish *Iec- and not Ieg-, thus my confusion.

C Gwinn