UK, 1860—very much, very intensely—‘billy-o’ occurs only in this phrase—it is apparently composed of ‘Billy’, pet form of the male forename ‘William’, and the suffix ‘-o’, used to form slang and colloquial nouns, adjectives and interjections
UK—‘the Beast from the East’ (2011): polar continental air mass, which brings wintry conditions—‘the Pest from the West’ (2012): mild air from the Atlantic, which brings strong winds and heavy rainfalls
Australia, 1966—typically Australian in character—alteration of the phrase ‘as American as apple pie’, with reference to the prominence of meat pie in Australian diet
USA, 1976—the outcome of a situation cannot be assumed—may allude to the stereotype of a large female soprano singing the final aria of an opera—from ‘church ain’t out ’till the fat lady sings’ (1976), itself from ‘church ain’t out until the singing is over’ (1872)
colloquial, Australia, 1910—‘the night’s (only) a pup’, or ‘the day’s (only) a pup’, means the night, or the day, is young—refers to ‘pup’ in the sense of a young dog
Australia, 1960—very fit and well, in robust health—the image is of a bull strengthened by his living in one of the semi-desert areas of Australia in which the principal vegetation is mallee, i.e., low-growing bushy eucalyptus
This phrase is applied to someone who is very strong and resilient in the face of hardship or pain. It originated in the USA in 1918; it has been used in British English since 1933.
USA—‘slobberknocker’ (1967): an American-Football player with a particularly aggressive style of play—from ‘slobber-knock’ (1964): of an American-Football player, to hit with extreme force—the image is of knocking the slobber out of somebody