ABSTRACT Colloquial Singapore English ('Singlish') is well known, among other features, for its class of discourse particles derived from substrate languages. These particles have been ascribed to various languages, chief among them Southern Min, Malay, and Cantonese. Previous research has also shown this class to be open to newcomers, with Lim (2007) concentrating on particles of Cantonese origin appearing in the 1980s. In this paper, I present evidence of a previously undocumented particle, bah, whose origins are suspected in Mandarin, a variety that has hitherto contributed only little to the grammatical structure of Singlish. Using corpus data complemented by data from online discussion forums, as well as responses to an online survey, the paper describes bah's pragmatic meanings and the socio-historical and sociolinguistic reasons for its emergence. [ABSTRACT FROM AUTHOR]