ar gyfeiliorn

== Welsh == === Etymology === From ar +‎ cyfeiliorn. === Adverb === ar gyfeiliorn astray mynd ar gyfeiliorn ― to go astray === Further reading === R. J. Thomas, G. A. Bevan, P. J. Donovan, A. Hawke, et al., editors (1950–present), “cyfeiliorn”, in Geiriadur Prifysgol Cymru Online (in Welsh), University of Wales Centre for Advanced Welsh & Celtic Studies