I’ve been enjoying the BBC TV series Last Tango in Halifax, a show which regularly sends me to the dictionary in order to decipher certain inscrutable British-isms, the latest being “don’t get all shirty birty (?) with me.”
Oxford Dictionaries online defines shirty as an informal adjective which means: irritable; querulous, i.e., ‘don’t get annoyed or shirty on the phone’.
Etymonline has only this to say: shirty adjective: "ill-tempered," 1846, slang, probably from shirt (n.) + -y (2), on notion of being disheveled in anger.
But where does shirty come from? And berty or bertie, is that merely decorative rhyming slang?