Abyssinia – I’ll be seeing you. A valediction that started during the Italo-Abyssinian war. Obsolete, but so Joyceanly satisfying that it is sometimes hard to resist.
Accidental(ly) on purpose – Deliberately, but with the appearance of accident: ‘So I put me hand on her knee, see, sort of accidental on purpose.’ (Literary locus classicus: Elmer Rice’s The Adding Machine, 1923.)
Arse – I need not define. The taboo is gradually being broken so that plays on the stage and on radio and television introduce the term with no protest. The American Random House Dictionary … is still shy of it, however, though not of the American colloquialism ass. Arse is a noble word; ass is a vulgarism.