(literally) to sit at a table; (figuratively) to establish oneself firmly in a situation—‘to put one’s feet under the same table with somebody’: (literally) to sit at a table with somebody; (figuratively) to associate oneself with somebody
every contribution towards a goal is valuable, regardless of how small it may be—UK, 1707—in Britain, particularly associated with Tesco, which has used this phrase as its slogan since 1993
various meanings, in particular: something with a larger capacity than its outward appearance suggests—UK, 1968—the name, in TV series Doctor Who, of a time machine outwardly resembling a police telephone box, yet inwardly much larger
the game of cricket played in the incorrect manner or improper spirit—hence, more generally, something contrary to traditional standards of fairness or rectitude—UK, 19th century
an oppressive, very confined or crowded space—UK, 1764—refers to the punishment cell at Fort William, Calcutta, in which, in 1756, the Nawab of Bengal reputedly confined British and Anglo-Indian prisoners
also ‘to be all thumbs’—to be extremely clumsy (i.e., lacking in manual dexterity)—19th century—variants of the original phrase ‘each finger is a thumb’, already proverbial in the mid-16th century
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
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