twll tin byd

== Welsh == === Etymology === Literally, “world's arsehole”. === Noun === twll tin byd m the arse end of nowhere, the back of beyond === Further reading === R. J. Thomas, G. A. Bevan, P. J. Donovan, A. Hawke, et al., editors (1950–present), “twll tin (din) byd”, in Geiriadur Prifysgol Cymru Online (in Welsh), University of Wales Centre for Advanced Welsh & Celtic Studies