# Rock around the old oak tree

I'm the reason why Ireland doesn't sink,
And what sometimes keeps people from the drink,
I'm not Fahrenheit, my choice tells you that,
Rotten rotten me, almost proved Fermat.

I gotta be...

... C O  R  K

The title, “Rock around the old oak tree,” refers to this riddle’s answer and first line in at least three ways:

Rock Around the Clock” and “Tie a Yellow Ribbon Round the Ole Oak Tree” are well-known rock songs and Cork Rock is a book about rock music in County Cork, Ireland.
Better— thanks to Ankoganit:   “rock” turned “around” spells “cork.”

I’m the reason why Ireland doesn’t sink,

Cork (a city, and its county) is in Ireland and cork (the bark of cork oak) floats.

And what sometimes keeps people from the drink,

Can’t guzzle without uncorking the bottle.

I’m not Fahrenheit, my choice tells you that,

I’m C  o r  K (Celsius or Kelvin), Jim, not an F (Fahrenheit).

Rotten rotten me, almost proved Fermat.

More thanks to Ankoganit, for solving the pyramidion of this riddle:

Two applications to “C O R K” of alphabetic rotation by ten steps produces “W I L E,” which almost spells “Wiles,” the last name of the mathematician who proved Fermat’s Last Theorem.

         Original             After                 After another
letter and           rot-ten                   rot-ten
alphabetical       (rotation by              (rotation by
position           10 steps)                 10 steps)

C    3  - - - -  13   M   13  - - - - - -  23   W   23
O   15  - - - -  25   Y   25  - - - - - -  35   I    9 (=35-26)
R   18  - - - -  28   B    2 (=28-26) - -  12   L   12
K   11  - - - -  21   U   21  - - - - - -  31   E    5 (=31-26)
+                                               +
Y   25  - - - -  35   I    9 (=35-26) - -  19   S   19

Frosting on the cake, from a comment by this puzzle’s author:
“Corky Rotscore proved Fermat’s Last Theorem”

• First revision will note how the answer to line 1 jibes with the riddle's title – humn Oct 21 '17 at 6:18
• Also, regarding the rotten clue: the past tense of cork somewhat crudely describes the n>2 case. – Lawrence Oct 21 '17 at 8:44
• I wonder who Jim is. (On Kelvin I like the story where when the Tripos results were posted he sent his man to see who was second place in the list, and was told 'Your are Sir!', the reason being Thomson at that time didn't revise a result he had discovered thinking it wouldn't be set, but the other guy did. Another one is when knighted he returned to local QUB and took over from a lecturer named Day. Apparently he was bad and when he left the students wrote on the board something like Thankfully Night has turned into Day.) – Tom Oct 21 '17 at 8:48
• Links have been added, @Tom, including one for the gratuitous "Jim" hail. Thank you for a rare riddle that I could even partially solve. The 1/4-O-Donnell in me got to join the fun. – humn Oct 21 '17 at 9:59
• – Rand al'Thor Oct 28 '17 at 0:15

I'm gonna guess:

Degree.

I'm the reason why Ireland doesn't sink,

I'm guessing the temperature (weather) not causing the sea to rise high enough to sink Ireland.

And what sometimes keeps people from the drink,

I checked the statistics and people with higher education drink more. So maybe it's a reference to how people without a degree (and lower pay) are financially kept from being able to purchase as much alchohol.

I'm not Fahrenheit, my choice tells you that,

I can only guess that's a reference to Europe using Celsius.

Rotten rotten me, almost proved Fermat.

Perhaps a reference to Fermat's Last Theorem and the mathematical degrees, when if greater than 2 with all positive integers becomes an unsolvable equasion. ()

• Good answer. The second line may have been clearer if asked 'And I'm the last light obstacle to drink' – Tom Oct 21 '17 at 11:10