This episode exposes theories behind the origins of  what we call pets. While 'cat' has its roots in the Old English 'catte' and 'dog' in 'docga,' the origins of 'guinea pig' and 'budgerigar' remain shrouded in mystery. Also explored are the meanings of the UK's favourite pet names including Luna, Milo, Lola, Bella and Simba, and a theory behind the idiom 'It's raining cats and dogs'.