UK, 1870—a very hard ship’s biscuit—refers to the fact that these sea-biscuits were particularly carried by Liverpool merchant ships; likens the shape and hardness of these sea-biscuits to those of pantiles, i.e. roofing tiles curved to an ogee shape
a dentist—World War Two—slang of the British armed forces—was soon adopted into (and came to be regarded as) Australian English—earlier synonyms: ‘fang-faker’ and ‘fang-wrencher’
UK—a general term of disapproval, meaning ‘unpleasant’, ‘dirty’, ‘nasty’, ‘ugly’, etc.—shortened form of ‘grotesque’—first recorded in (and popularised by) A Hard Day’s Night (1964), a musical comedy film starring the Beatles
UK, 1980—denotes someone or something that is unwelcome, unpopular, etc.—first recorded in a remark by the Scottish comedian Billy Connolly, but perhaps originated in Royal-Navy slang
UK, 1933—a jump made with a parachute—hence also the verbal noun ‘brolly-hopping’ and the verb ‘brolly-hop’—‘brolly’ (university slang, late 19th century): a clipped and altered form of ‘umbrella’
USA, 1906—a man who fixes something, especially a man who, often illicitly, arranges matters or sets up deals—cf. ‘fixer’: one who, often illicitly, arranges or adjusts matters