No. 53.

The opposite of 'hey presto' (the magician's call to make something disappear) is 'hey jingo', which makes something disappear.

(Source: Qikipedia, the Twitter feed for the QI elves.)

No. 11.

Mufti, a word now meaning casual clothing, originally was an Arabic term for a scholar of Sharia Law. It gained its current definition via the British Army - mufti was the vaguely Eastern clothes worn by off-duty officers.

(Source: Wikipedia. Researched as curious to the ethnic origins of the word.)

No. 8.

Auld Lang Syne roughly translates as 'old time since', 'days gone by' or 'long long ago'.

Incidentally, contrary to popular belief, the song is not written by Robert Burns.

(Source: Trivia website. Verified by Wikipedia. Latter fact explored on QI.)

No. 7.

The phrase 'pool your money' comes from a French game in which you chuck stones at a chicken.

Each player would put their money in a pile before taking turns to attempt to hit the bird. Whoever got it first won all the cash. The French for chicken is, of course, 'poulet'.

(Source: The Etymologicon by Mark Forsyth. Heard on Radio 4's Book of the Week.)