What does Emma stand for in Ack Emma and Pip Emma?

Ack Emma - is a British slang term for "a.m." as in ante meridian. The phrase derives from a British signalman's letter code, in which Ack stood for A and so on. This is also where the word Ack Ack for anti-aircraft (AA) fire comes from, as well as the origin of the companion term Pip Emma.

http://people.sc.fsu.edu/~jburkardt/fun/wordplay/weird_words.html

The letter m. Ack Emma = a.m. (from the Latin ante meridiwm, before midday, morning); Pip Emma = p.m. (from the Latin post meridiem, after midday, afternoon).

http://people.sc.fsu.edu/~jburkardt/fun/wordplay/weird_words.html

Ack Emma - is a British slang term for "a.m." as in ante meridian. The phrase derives from a British signalman's letter code, in which Ack stood for A and so on. This is also where the word Ack Ack for anti-aircraft (AA) fire comes from, as well as the origin of the companion term Pip Emma (see PG Wodehouse, somewhere).