" Ts'il?os Park (a.k.a. Ts'yl-os Park) " established per Order in Council 0064, 12 January 1994, containing 233,240 ha. more or less. Conversion of OIC to Statute designation per Bill 53: Park Amendment Act 1995, 13 July 1995. Form of name changed to Ts^ 'il?os Park (ie. to add a circumflex ^ over the first s) per Bill 29: Park Amendment Act 1997, 23 July 1997, as requested by the Xeni Gwet'in First Nation.

Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office

A Chilcotin orthography has been devised by linguists, containing special characters that are not readily reproduceable, hence the writing system is undergoing rapid modification by writers of the language: "Ts^'il?os" - where the first "s" is presented with a circumflex to modify the sound of the vowels that follow, the apostrophe denotes a glottal stop, and where the question mark is presented without the dot and also denotes a glottal stop. The common pronunciation, resulting from the alternate spelling appearing in print, is "SIGH-lows".

Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office