Slap up meal.

[netty.m]

Why do we say "slap up meal"?  Also why do we call it a square meal ?  Sorry for being greedy ( ha ha ) and asking 2 questions.

[Quizmonster]

Click http://www.wordorigins.org/wordors.htm#squaremeal for an explanation of square meal. Slap-up is a more recent variation of 'bang-up', meaning 'excellent'. The word' 'bang' here was used in the same way as it is in the phrase 'bang in the middle'. This suggests it is exactly there or exactly right. Thus, bang-up and later slap-up mean 'just the ticket' or 'the very thing' etc...ie a wonderful meal, for example.