UK, 1941—a fighter pilot in the Royal Air Force; also used by the military land forces of any member of the R.A.F.—originally referred to WWII advertisements for Brylcreem hair cream, featuring a fighter pilot
to get a severe beating—popularised in UK & Ireland in the 2nd half of the 20th century through its use in chants by supporters at Association-Football matches, chiefly to threaten opposing away supporters
UK—an ambulance (i.e., a vehicle designed to carry sick or injured people)—originally (Royal Air Force slang, 1921): a specially equipped airplane for carrying sick or injured people
a married woman living apart from her husband (18th century)—originally (16th century) an unmarried woman who has borne an illegitimate child—alludes to a bed of grass as a typical place for illicit sexual intercourse
UK—anything which discourages or inhibits sexual activity—originally (1943, British military slang): the sturdy, practical and unattractive underwear issued to female service personnel
genetically modified food—but had been used earlier by members of Weight Watchers in the sense of food one is addicted to—in reference to ‘Frankenstein; Or, The Modern Prometheus’ (1818), by Mary Shelley
a person who whines or complains—UK, 1769, humorous—‘Peter’ is used as a generic forename, and the adjective ‘grievous’ (meaning ‘aggrieved’) is treated as a surname