The Collaborative International Dictionary
Gaulish \Gaul"ish\, a. Pertaining to ancient France, or Gaul; Gallic. [R.]
Douglas Harper's Etymology Dictionary
1650s (adj.); 1660s (n.), from Gaul + -ish.
Wiktionary
Wikipedia
Usage examples of "gaulish".
Small numbers of Roman cavalry - not the wild Batavian horsemen of the cohorts or their Gaulish auxiliary comrades - covered the margins, preventing an attack from the rear.
Romans called Turris Ordinis, and the Gaulish Celts called Nemtor, which once stood on the lofty plateau, but is no longer in existence.
On the other side of the Palmyrene boy, one of the Gaulish wizards was almost grinning, blowing frosty breath up into the air.
Vicarius Columella professed to find this tale fascinating, so I gave him a much-reduced version of the events which had led me to enroll as a mercenary in the Gaulish auxiliary.
The reply which the senate made to these deputations and to the Gaulish prince, who had left Rome, was to the effect that with regard to the subjects of complaint, they were quite unaware that such things would happen, and if they had happened they did not sanction them.
He heard Viridovix swear in Gaulish, caught the name of the Celtic horse-goddess Epona.